This sounds all too familiar. ENFPs needing constant external validation, no....
Some practical suggestions and some of what resonates with me. The latter first:
I struggle with the idea of looking outside in deciding how much. On one hand, getting external opinions and not thinking of ourselves as omniscient is a real strength, a sign of humility, a sign of being open to criticism and one of the things I love about maturing as an ENFP. The problem is when we don't use this external input for the purpose of reflection at all but instead need it simply to stroke our ego. You clearly have a well developed Fi. It likely pointed to guilt in the situation you mentioned. In my case, I know when I have done something which may have hurt/harmed someone else and I am very harsh on myself. To drown out this unbearable Fi noise, I seek justification from within and without. From within, it's in the form of using past wrongs from the other side -- well, this is what
they did which completely deserve my actions. There. Nicely balanced. Doesn't work, does it? Fi still complains
From without, it's getting reassurance from friends, family, anyone who will listen to reinstate that idealistic view of ourselves as caring human beings. From my own experience, that doesn't work either. When I
know I'm at fault, I know. People validating my need for reassurance just lose my trust in the long run. When I've come out of the "woe is me, I've been wronged" loop, I can see the situation more clearly and then I not only dislike my own weakness, I also dislike the enablers. Your ISTP guy is an asset in that he speaks truthfully. That's rare.
You already know the answer - Fi is giving it to you without you asking for it
. The key as others have said is not drowning in it. Striking that balance between being able to listen to Fi and not getting completely lost in what it reflects. Ultimately, it was a small transgression among friends. Friends forgive and forget. Those who don't won't last very long around an ENP. Your strong moral compass is a strength. Being genuinely sorry and expressing it, resolving to do better in the future and moving on is all you can do. Other people control how they react.
Practical advice:
When I don't want to hear what I already know (I did something I regret) because it's only going to add to the Fi noise, I ask the person I turn to to just listen. They don't have to give me the honest truth if I'm not ready and they don't have to lie or sugar coat it either. The best answers are the ones we find for ourselves and sometimes as an extrovert and a rambly one at that, it's nice just to have someone who listens patiently as I figure out how
I feel about it all so that I can Te through -- sort, file, make a decision on how to resolve the problem and move on.
I am a very dependable friend but I am also regularly tardy for social engagements and sometimes feel hemmed in by my own plans so I have to change them at short notice. While my friends are very understanding, I don't want to disappoint them or myself. I try to not over commit and keep the few commitments I make. I'll still be me but I have a cut off by which a decision must be made and the person informed. Beyond that, I stick to the original commitment. The friends appreciate the effort but it's also to keep me sane. I don't like disappointing myself. That crazy, relentless Fi... it just won't shut up.
Hope you're feeling better about it all.