Asklemmy

I understand how you feel. The first step to reduce the frustration is to try and give it less importance: as you said yourself, it's not falling in love, it's just infatuation. Your brain is confusing attractiveness to another person (physical or romantic) for a deep connection that doesn't come at first sight (despite what movies and tv would make you believe) but develops in time.

You will be attracted to a lot of people in your life (assuming you're not aromantic or asexual) and, with time, you'll realize if you went deeper in many of these situation, the attraction would disappear, because the shallow opinion you have of a person you are not dating is very difficult to get right, and usually filtered positively by your monkey brain that just wants to formicate.

Of course trying and deepening these attractions would help you realizing this, which might not be easy if you have difficult approaching other people, but try and reflect on similar situations in the past and think about them cold-hearted: to how many people are you still infatuated? Don't you see now the "bad things" that you brain was hiding and that don't make you two really compatible?

Eventually it just becomes a nuisance. I don't know if you can change it, but you can accept it and it will bother you less if you understand the mechanism behind it.

Maybe you just feel affection-starved and in these situations it's easy to attach to ideas of relationships rather than real ones. Nothing weird of course, everybody do it is some way or another. It's a combination of social brain and (according to your comnents) low self-esteem.

Of course these are my 2 cents according to personal experience, a therapist would you help you more with that.