When I see someone(good or bad, ugly or beautiful), I start feeling that I have become that person and ultimately get disturbed by this thought. I start fighting with this thought till the time I start believing that I am what I was earlier and nothing has actually changed in me.
Please tell me what kind of problem this is and how to get rid of this problem ?

Also, I always feel sad and keep on thinking about one or the other thing, this also keeps me disturbed.