External circumstances? Er, I would disagree here. The INFJ internalized dilemma is 'I don't know enough to attempt this yet' and the INFJ will be side-tracked in a lot of busy work related to the task, but none of it really effective. This is especially prominent in an INFJ engaged in the infamous Ni-Ti loop.
And the INFJ will beat themselves up forever for it if they realized they had engaged in self-sabotaging behaviour. Failure, like we've established above, is not an easy pill for any Inuitive Judger to swallow. The INFJ's penchant for having trouble letting go doesn't just stop at relationships, after all. If the project or task was seen as essential, and it wasn't completed because of an INFJs own incompetence, it won't be so easily abandoned as you suggested. It will come with a lot of pain that will leak into everything. The problem for INFJs isn't 'it's impossible,' it becomes ' I didn't try, because I should have tried given the information I had at the time.'
Deciding whether or not to put my heart into something is definitely a dilemma I do face. Once I decide to do something, I am typically very determined and very focused. There are times in reaching my goal that I will be mentally exhausted or feel discouraged, where I might not be exactly "on schedule," but I won't let myself get to a point where I'm in danger of failing. However, sometimes when I'm already "behind schedule" and something unexpected happens, that's when I might end up failing. The circumstance might not be entirely external, but there will be something else that I become fixated on, obsess over, or become depressed about. For example, my goal during my second semester of college was to get all A's. That semester made up the last few months of my relationship with the INFP I had spoken of. Our relationship was starting to go downhill. Academically, the semester was off to a usual good start, my average was an A in every class. It was about mid-semester that he just especially didn't seem as "into it." I remember having an overwhelming feeling that there was something going on between him and one girl in particular. It was so obvious to me, though there was no "proof" and it bothered me greatly. I did everything I could to find some kind of peace with the situation. I eventually confronted him about it directly once, pointed out some of his behaviors that made me believe he might have feelings for her, and he said there was nothing going on, that it wasn't like that at all. But my gut just couldn't believe what my boyfriend said, but I tried. I found it increasingly difficult to focus on my school work because of the emotional stress the relationship caused me. I was also very concerned he might not pass his classes. He was intelligent, but impractical and a horrible procrastinator. I helped him with several last minute projects, becoming more and more irritated each time I was asked. I couldn't believe how irresponsible he was and it probably made me more stressed out than him. Though I willingly helped him, I often felt used because I knew he wouldn't do the same for me. He did much more serious and hurtful things that eventually forced me to leave him. He never thought about how his actions might hurt other people, how they might make the person he "loves" feel like dirt. Maybe it sounds pathetic that a relationship of only a year and a half would have so much control over my life, but I took it seriously. We were very much a part of each others lives and we (used to) do everything together. I was committed and gave it everything I could and he didn't. So, this combination of external and internal distractions wasn't conducive to studying obviously and I didn't get straight A's. I instead got all A's and one B... For a long time I was very disappointed in myself and saw only what I didn't accomplish. I always just told myself I didn't try hard enough. I eventually got over it and realized even though I didn't reach my goal, I still did really well, especially considering what a difficult time that was in my life (several other serious things not related to the relationship weighed on my mind at this time too.) The end result wasn't my best work overall, but it was my best given the situation, I tried as hard as I could at the time. I learned to stop seeing what "wasn't my best work" as "not trying hard enough." I worked alone, hard and honestly. And I learned to find pride in what I did manage to accomplish. My ex cheated his way through some classes and even in using me, his average for the semester was less than a 2.5 and he had to repeat a class because he did not give it his best. And his dishonestly ran deep, as it turns out he did have feelings for that other girl all along.
Unfortunately, during other semesters I ended up falling short of my goal again. Being so close with all A's and one B. There would come a point in the semester where I would say "Well, it's not really realistic to still try to get an A," but there would be a little disappointment in myself at the end of each term still. There were serious situations (severe illness/complications from medication and a death in the family) that interfered with my ability to function normally, but at times I felt that didn't excuse my "failure." Looking back now I accept that I didn't put forth the effort I would have liked to because I really
couldn't.
Apathy. Depression. Feelings of worthless. Yes, I would agree. Doesn't mean they 'abandon the project and move on,' though. An INTJ might, but an INFJ wouldn't pass up the opportunity to crucify itself for not being the right person for the job first.
I was saying just that they abandon the project. They might not really move on mentally, but they're no longer actively engaged in the project. It doesn't come naturally, but I've learned to recognize when to cut my losses. Eventually I did make straight A's. It was the perfect storm of problems that were less invasive to studying, determination, putting everything else in my life on the back-burner, and I think just luck. It was absolutely awful (especially being on a 6 point scale). I was completely miserable the whole time. Sure, I got what I wanted, and I felt accomplished, but it didn't make me happy. What I sacrificed wasn't worth what I got in return. So the next semester I didn't put the same pressure on myself. I hoped to get all A's again, but soon realized after the first test in my law class (and how much everyone struggled in the class) that getting an A would require an unrealistic amount of time and effort. Once I realized this I said "Ok, well I'm not going down that same dark road again. I can live with a B." I very quickly abandoned my initial goal and it made life much easier. I was content with my grades at the end of the term. It took me a long time to be able to do this and I had to really change my way of thinking, but I did still.
I have always been very hard on myself, the default nature of an INFJ is usually to attack the self, but this
can be changed. I might be very upset about something initially, but I've learned to just tune out my Fe for a while and let my Ti take over so I can process my mistakes more rationally and effectively. I allow my feelings to come back into the matter at a later time when they can be used positively. If I hadn't learned how to do this, I would never achieve a sense of closure. I don't know many INFJ's in person, but I don't see this as being an uncommon way to address problems. I see my approach to achieving goals and accepting failure now as very different from what you describe, though a lot of what you have said was somewhat true of me in the past.