I think I'm approaching the question a little differently than others, but here it goes:
People usually have expectations of me when it's in an area that I've shown proficiency in. For example, I'm usually asked for help in areas that require creativity, logic, or problem-solving skills. It only gets to be too much when I feel like people are taking advantage of me and could probably do whatever it is themselves if they tried hard enough.
A specific situation in which someone has unrealistic expectations of me involves a close ESFP friend of mine. She manages to create all sorts of problems for herself and often comes to me about them because I usually give pretty good advice. The problem is that she now expects me to always have some sort of solution for her. She almost always says "tell me what I can do to fix... [insert problem here]". It's a lot of pressure to put on one person and can get very tiring, especially because I feel like I'm just repeating myself every time she comes to me for help.