10 Effects of Sins in Islam
Question

I did Hajj for myself, and a few months after Hajj I still had not seen any sign that my Hajj was accepted in the sense that I turned to worship more. On the contrary, I committed a lot of sins. Last year I resolved to do Hajj on behalf of my mother who has passed away. I asked one of the shaykhs (scholars) and he said that I should do Hajj on her behalf as I had intended, and I should pray a lot for forgiveness and beseech Allah. So I did Hajj on behalf of my mother, traveling with one of the groups. During Tawaf Al-Wada’ (farewell circumambulation), the overcrowding was very severe, so we did one circuit (of Tawaf) and part of another circuit, then we went up to the roof, because of the severe overcrowding. Because of the overcrowding we were not quite sure of the exact spot where we had stopped on the lower level, but we did our best to make sure that we started our Tawaf on the roof from the place where we had stopped on the lower level, and we continued with our Tawaf until it was completed.
After my last Hajj, if I committed any sin – and I did many of them – I felt some tightness and constriction in my chest, and if I did any act of worship or obedience I felt happy and full of sincere feelings towards Islam and its people at this time… I am worried about the two pilgrimages and about the Tawaf. Please advise me, may Allah reward you.
Praise be to Allah.The Dangers of Sin in Islam
We advise you to keep away from all sin, minor and major, and to beware of it and avoid it, for sin is bad news for the one who does it.
Consequences of Sin in Islam
We will quote here some of the effects of sin, as described by Ibn Al-Qayyim (may Allah have mercy on him):

Being deprived of knowledge for knowledge is light that Allah causes to reach the heart, and sin extinguishes that light. When Ash-Shafi`i sat before Malik and read to him, he admired him because of the intelligence, alertness and understanding that he saw in him. He said, “I think that Allah has caused light to enter your heart, so do not extinguish it with the darkness of sin.”
Being deprived of provision. In Musnad Ahmad it is narrated that Thawban (may Allah be pleased with him) said: “The Messenger of Allah (peace and blessings of Allah be upon him) said: ‘A man is deprived of provision because of the sins that he commits.’” (Narrated by Ibn Majah, 4022, classed as sound by Al-Albani in Sahih Ibn Majah)
Sense of alienation that comes between a person and his Lord, and between him and other people. One of the Salaf (righteous predecessors) said: “If I disobey Allah, I see that in the attitude of my riding beast and my wife.”
Things become difficult for him, so that he does not turn his attention towards any matter but he finds the way blocked or he finds it difficult. By the same token, for the one who fears Allah, things are made easy for him.
The sinner will find darkness in his heart, which he will feel just as he feels the darkness of night. So this darkness affects his heart as the physical darkness affects his vision. For obedience is light and disobedience is darkness. The stronger the darkness grows, the greater becomes his confusion, until he falls into innovation, misguidance and other things that lead to doom, without even realizing, like a blind man who goes out in the darkness of the night, walking alone

This darkness grows stronger until it covers the eyes, then it grows stronger until it covers the face, which appears dark and is seen by everyone. `Abdullah ibn `Abbas said: “Good deeds make the face light, give light to the heart, and bring about ample provision, physical strength and love in people’s hearts. Bad deeds make the face dark, give darkness to the heart, and bring about physical weakness, a lack of provision and hatred in people’s hearts.”

Deprivation of worship and obedience. If sin brought no punishment other than that it prevents a person from doing an act of worship which is the opposite of sin, and cuts off access to other acts of worship, that would be bad enough. So the sin cuts off a third way and a fourth way and so on, and because of the sin he is cut off from many acts of worship, each of which would have been better for him than this world and everything in it. So he is like a man who eats food that is bound to cause a lengthy sickness, and thus he is deprived of many other foods that are better than that. And Allah is the One Whose help we seek.
Sin breeds sin until it dominates a person and he cannot escape from it.
Sin weakens a person’s willpower. It gradually strengthens his will to commit sin and weakens his will to repent until there is no will in his heart to repent at all… so he seeks forgiveness and expresses repentance, but it is merely words on the lips, like the repentance of the liars, whose hearts are still determined to commit sin and persist in it. This is one of the most serious diseases that are most likely to lead to doom.
He will become desensitized and will no longer find sin abhorrent, so it will become his habit, and he will not be bothered if people see him committing the sin or talk about him.

For the leaders of immorality, this is the ultimate shamelessness in which they find great pleasure, such that they feel proud of their sin and will speak of it to people who do not know that they have done it, saying, “O so and so, I did such and such.” Such people cannot be helped and the path to repentance is blocked for them in most cases. The Prophet (peace and blessings of Allah be upon him) said: “All of my ummah (followers) will be fine except for those who commit sin openly, and that includes cases where Allah conceals a person’s sin, but the following morning he exposes himself and says, ‘O So and so, I did such and such last night, so he shamelessly exposes himself when all night his Lord had concealed his sin.” (Narrated by Al-Bukhari, 5949 and Muslim, 2744).

When there are many sins they leave a mark on the heart of the person who commits them, so he becomes one of the negligent. As one of the Salaf said, concerning the verse–

{Nay! But on their hearts is the Ran (covering of sins and evil deeds) which they used to earn.} [Al-Mutaffifin 83:14 – interpretation of the meaning] – this means sin after sin.
How this starts is that the heart gets stained by sin, and if the sin increases then the stain grows bigger until it becomes the Ran (covering of sin and evil deeds), then it increases until it becomes a seal, and the heart becomes covered and sealed. If that happens after a person had been guided and had understood, then his heart is turned upside down, and at that point the devil gains control over him and directs him as he wants.
Hajj and Repentance: Cleansing the Heart after Sin
You say that you did Hajj and did not see any signs of acceptance, rather you committed a lot of sins. The answer to this is that acceptance is from Allah, and no one can be certain whether your deed has been accepted or not.
The believer does righteous deeds and does not know whether Allah has accepted them or not.
Indeed, Ibn `Umar (may Allah be pleased with him) said: “If I knew that Allah had accepted even one good deed from me, death would be the most dear thing to me, because Allah says, {Verily, Allah accepts only from those who are Al-Muttaqun (the pious)} [Al-Ma’idah 5:27 – interpretation of the meaning].”
Man is required to do a great deal of righteous deeds, and to strive to make sure his actions are in accordance with the commands of Allah and His Messenger. In this manner he will free himself from any blame, then he must ask Allah to accept his deeds.
So if you did you Hajj properly and avoided everything that is forbidden during Hajj, then you do not have to repeat it. As for your falling into sin, that has nothing to do with the validity or otherwise of your Hajj, but you will be brought to account for it, so you must hasten to repent from it before your appointed time (of death) comes.
Can Tawaf Be Interrupted?
You say that you did Tawaf then went up to the roof because of the overcrowding.
This is the issue of continuity in Tawaf. The Standing Committee was asked a similar question and replied that there is nothing wrong with interrupting Tawaf and completing it on a higher level (of the mosque). (See Fatawa Al-Lajnah Ad-Da’imah, 11/230, 231, 232)
With regard to the start of Tawaf, it should begin in the same place where it ends. With regard to your efforts to figure out the place, if it is not possible to be certain then you should act according to what is most likely to be correct, because the Prophet (peace and blessings of Allah be upon him) said, concerning one who is uncertain as to whether he has prayed three rak’ahs or four, “Let him try his best (to work it out), then complete it on that basis – i.e., he should base it on what he thinks is the case – then let him say the Salams (two salutations at the end of the prayer, one to the right and one to the left)and do two prostrations after he says the salams.” (Narrated by Al-Bukhari, 401 and Muslim, 572; see also Al-Sharh Al-Mumti`, 3/461)
Based on the above, then your completing your Tawaf on the roof and your striving to start from the place from which you interrupted your Tawaf are both fine in sha Allah.
For more details, please see the following answers:
Means of expiating sin
Sinning openly in Islam
7 Major Sins in Islam: What Are They?
What are the sins committed when one is alone?
Is punishment from Allah one of the consequences of sin?
And Allah knows best.