Humans naturally pay attention to what the people around them do and judging what they see quickly follows. Our minds promptly tell us what others should and must do—how they absolutely need to change.
This, inevitably, leads to problems because others are free to do as they wish. They simply don't have to comply with our demands. People can choose to do what we see as poor behavior, mistakes, and even immoral and illegal acts. Of course, this behavior can carry steep consequences, but even so, this does not mean that they must not have chosen it.
People generally do what they believe to be the right thing for them. From their point of view, their behavior is acceptable—and while we may not agree with their "logic", it is a losing battle to insist that they should see the world the way we see it.
Another way to phrase this is to accept that there are no absolute "should's" or rules that people must live by. People are not trains on tracks that must go where they have been compelled to go. Even if you believe in a religious doctrine that includes strict laws of behavior, people still have the option not follow them.
Often, in our anger, we might wish to punish people ourselves for their not behaving as we dictate—as if we are angry gods who can smite and damn the wayward mortals. But this arrogance will, in the end, cost us much, and change others little.
The only sensible solution is acceptance of the other—to allow them to be who they are, even if we disapprove of what they are doing. Acceptance will end the little war your mind is waging in a futile attempt to change what cannot be changed.
When you are angry at (or hurt by, or disappointed in…) someone, evaluate your thoughts and beliefs about the person. What are you demanding to be different about them? Whatever it is, let it go. Accept that they are who they are and that they do not have to change. Once you accept that, dealing with them will be far easier. You will be more effective doing so because you have already made your peace with the fact that they may not change.
This does not mean that you shouldn't seek to influence others for the better when you can. There are some circumstances when we are able to have a powerful influence on others. Particularly when we are in positions of leadership and authority (such as a being a parent, teacher, boss, governor, prison warden, or emperor). But even in these cases, you would be better of accepting that others have free will.
Also, I do not mean to imply that acceptance of others is an easy task. This is not an immediate process. Acceptance always takes practice to become aware of your thoughts, noticing your demands, and gently reminding yourself of what is and what is not up to you.
Anger. This idea will help you avoid the futility of trying to change what you cannot and the bitter resentment that follows. that will come with anger. If you allow yourself to damn others and insist that they be different than they are, you are the one who will suffer. The anger will eat away at you and you will find that others are less and less motivated to seek out a connection with you. This, in turn, could lead to even more anger, and a downward spiral can begin.
Tranquility. Acceptance of others will help you find peace of mind. Nothing is more disturbing than demanding that someone else or some aspect of the world be different. Allowing it to be as it is will preserve your energy for those things that you can change.
This idea comes pretty much straight out of Albert Ellis's writings relating to Rational Emotive Behavior Therapy. Ellis discussed two irrational beliefs that result in much human suffering: Demandingness or the belief that the world and the people in it must be what we decide that they should or must be, and the idea that Conditional ratings of the Self (and Others) lead to disturbed emotions.
Next: You Are Not Your Thoughts. You Are Not Your Feelings.