I don't know how much to expect

 

“If you expect nothing from somebody you are never disappointed”

It might have happened to you often. You developed a habit of having unrealistic expectations based on a small interaction. Something like an incident where someone was nice to you for a moment and you thought they were kind. Or even something like a regular place where people help you out so you develop the thought they are helpful and will help further too. Or even an interaction with someone you consider your friend, ending up doing a slightly flirty or romantic action which leads to thinking of you being in a relationship further. 

It does not seem like a problem until very late. You start having an expectation of this happening further and you keep anticipating similar actions. And when it does not, you tend to feel disappointed or even something like you were led on. But was that the case? Or was it made into something different in your mind based on a single interaction. And thus the sadness and anger or even hurt. 

Well, I'm sorry but we can never define anything based on just one incident. We always have to confirm it by communicating or even noticing familiar patterns. This is how you know the difference between an incident and actual feelings. It may seem difficult to have that conversation but it is very important, because you need clarity. Or else the over thinking might change it into something it's not and develop an unhealthy relationship. I hope this makes a difference in understanding.