How to prevent self-deception? I have recently attended my first Vipassana 10-day course. I observe the moral precepts fully, practice diligently and attempt to proceed wisely on the path. I came into contact with Vipassana because of my ex, who, both in showing me to the path and in harming me, has been my precious teacher. In harming me, in failing to observe the fourth precept and sila, in seeking passion as a distraction from his suffering and a confirmation of his ego, without apparently being aware of this and even if being aware, not changing his behavior, my ex has caused me concern with regard to my own attempts at leading a proper life. I know I am not in a position to help my ex, as he has harmed me (also, I tried and he reacted with hostility), so what I am left with is the striking fact that this amount of delusion is possible in someone who calls himself a serious Vipassana meditator, which worries me with regard to my own practice. If someone who has been practicing for over 10 years thinks they are aware and are everything but, what am I going to do? I have fled into passion as well, in a quest for distraction from suffering as well as from a need for guidance and affirmation of my own ego. 
The obvious answer is to truly feel and accept painful feelings without reacting by fleeing into passion. But these impulses are strong and the mind is clever. What can I do to prevent this behavior? Can there be a mistake in the meditation practice itself that causes such obscurations to persist?

Additionally, I do hope to find a partner who observes truthfulness towards himself and others. How do I go about avoiding the blinding capacities of passion and idealistic desires in judging any such “romantic" situation accurately? I imagine working on one’s own mental and emotional hangups will diminish obscurations — how is one advised to go about this other than meditating? 

I know these are big and difficult questions. Any and all input is appreciated.
If someone who has been practicing for over 10 years thinks they are aware and are everything but, what am I going to do?


I think this issue you are raising is not really related to Buddhist meditation practices but to the individual. Some individuals, be they Buddhist or non-Buddhist, religious or non-religious, have a keen sense of not harming others &amp; being responsible towards others. Others do not.

That said, about Buddhism, my impression is cultural Buddhism, both Western &amp; Asian, is quite weak in its explanations of sexual misconduct to its lay followers since I get the impression monks don't want to put pressure on people by over-moralising. Therefore, it can be expected that people may practise Buddhist meditation for 10 years but have no real sense of the purpose of the precepts. In fact, there are enough Buddhist teachers that practise sexual misconduct. 

Sexuality is a very strong emotion/drive thus many people struggle to manage it.


  The obvious answer is to truly feel and accept painful feelings without reacting by fleeing into passion. But these impulses are
  strong and the mind is clever. What can I do to prevent this behavior?
  Can there be a mistake in the meditation practice itself that causes
  such obscurations to persist?


There are probably many suggestions to this question. One suggestion is to reflect on (think about) what benefit &amp; what harm will come from impulsive fleeing into passion? Will impulsive passion really help yourself? Will it really help the other person involved in the impulsive passion? Or will it create more hurt, more confusion, more regret? Is it really something you really want to do?

Buddhist practises about wise reflection are described in MN 61 and MN 19.


  Additionally, I do hope to find a partner who observes truthfulness towards himself and others. How do I go about avoiding the blinding
  capacities of passion and idealistic desires in judging any such
  “romantic" situation accurately?


As has been mentioned by Chris, the teachings in Buddhism about finding the right partner are not based in "romance". Instead, they are based on determining what your life goals &amp; values are and then finding a partner that can fulfil/meet your life goals &amp; values, i.e., a partner that shares your same goals &amp; values. 

This includes things many take for granted, such as having children. There are occasions when two people are together, romantically, for many years and suddenly one person raises their want for children and the other person objects to this. Ideally, the matter of having children should be sorted out before beginning the relationship. 

Thus, Buddhism does not really recommend get "romantically" or sexually involved with a prospective life partner before determining whether that prospective partner is suitable. It may sound very unromantic &amp; clinical but I assume it is like interviewing another person for a job. An employer does not employ a prospective employee until determining &amp; assessing the suitability &amp; qualifications of that person.

Often, this is how traditional cultures operated. Parents would get together &amp; assess whether a partner was suitable for their son &amp; daughter in marriage. The Buddhist approach is similar, i.e., more rational or cerebral rather than "romantic". 

Once "romance" (sex) occurs, that itself starts to make the situation less flexible since two people become attached to each other sexually (with the various demands &amp; expectations) even though they may not be suitable in terms of individual aspirations or temperament.  

Thus, Buddhism encourages the development of 'metta' (friendliness; loving-kindness). We should learn to relate to all people as 'friends' first; putting their welfare first. In meeting a prospective partner, ideally, we put friendship first. We become friends for a significant amount of time before committing to romance. 


  I imagine working on one’s own mental and emotional hangups will diminish obscurations — how is one advised to go about this other than
  meditating?


This can be done by learning about &amp; reflecting upon the Buddhist teachings about relationship. By doing this, we can learn about the mistakes we make in our past relationships &amp; the way forward for the future.

For example, if we can see the necessity of the Buddhist qualities prescribed for a suitable partner, we can realise our previous partner never did have the qualities or abilities to fulfill our expectations. But doing this, we may stop blaming them &amp; instead focus on our own choices.  

The main teaching of the Buddha can be read in AN 4.55 however the link already provided explains the main relevant teachings of the Buddha.