Being precise is different from being pessimistic. I think one can easily mix one with another. I mean, sometimes we think we've been so exact about people's behaviors, thoughts and reactions and we've been protective about our rights but the bottom line is that we've been actually picky or paranoid in many of those cases.
Well, imagine if we accept that we've been even right in 6 out of 10 of the things that someone did to us and they had something to do with our lives,emotions and benefits. I still think, that 6 will NOT worth it to make any kind of big deal out of it. When there is a strong possibility of making 4 mistakes from the whole 10. Besides, it shows we are allowed to make mistakes in the world that over millions of scientific facts are based on trail and error. So why we should not just let go another's mistakes. It's a fair deal, isn't it? Especially when we think of the overall results which are to love others and to be loved. It's just healthy to look at the nice parts that each person at least has one for sure. It's not always easy but I do believe that is an artistic talent that one possesses.
I said all these to say that I'm afraid of negative people and am a big fan of optimistic ones and eager to be like them.