Have you ever been there?

I don't know why people usually get a very positive idea about me only after a short acquaintance. Though this should be a good thing, I'm sometimes not sure if it really is. This because it makes people expect from me more than what I'm actually capable of, and when I fall short of their expectations, they're disappointed and in turn I am depressed. Sometimes I get confused, am I really that good or I just seem this way. Am I really that smart or they're just expecting me to be so? Am I feeling this way because I don't have enough confidence in myself or they are the ones who are fooled? Have you ever experienced this?