Gut feelings

Has it ever happened to you to meet someone for the first time and at that exactly moment you feel you already know what the person is like?...well, this happens to me frequently and unfortunately, I was wrong in a few times. And I say unfortunately because when I have this sort of gut feeling I am predisposed to behave in a certain way with that person and not being just me. I am nobody to judge anyone or to say what is right or wrong, but I can`t help this sensation. I feel like I already know what is going to happen and I prefer avoiding some situations and let the things how they are.
I consider myself a good person but I know I have lot of defects which in some cases I try to correct them.
A few times I met people who I considered my friends, but then these people disappointed me by being cynical and dishonest. I`ve always been a direct person and whatever comes to my mind at a certain moment I say it without thinking, and perhaps that is why I seem to be unkind. But I prefer doing this rather than talking about people behind their backs. However, I think it is good giving opportunities and not being so defensive because I am not perfect and I know I make mistakes all the time and I`m sure I would like to have another chance if I do something wrong.