In many cases, if we like somebody or interested in a person, we unintentionally think this person is very similar to us. This misconception and bias always lead to disappointment when we realize this is not the case.
I have been overestimating my friend for more than two years.Recently, I found out she actually doesn't really know what I am talking about in most of the time. I guess things are more clear when one's step back and look it from a distance. Just like we do not stand under the fireworks because a clear picture doesn't show from that perspective.
Not to overestimate or underestimate a person is quite difficult especially when we are facing with somebody either we like that person a lot or we don't. But a suggestion, probably is to set our mind neutral and observe a person overall behavior before we dive into any emotional feelings.