I find it strange that because we are human, we have so much ability to do so much in the lives of others yet our flaws make it possible for us to do so many stupid things. In addition to none of us being perfect, we proceed to make life more complicated. Guys can say that girls complicate things unnecessarily but let me just say that guys aren't completely innocent either.
Speaking from a personal point of view, I know that it's so easy to just assume the worst of someone. Luckily it's something that is a choice and we have the ability to control. Recently I've learnt that there's a gap between what we expect and what we experience. We can choose to fill the gap with either "assuming the worst" or "believing the best". It's the most common thing just to assume that people will let us down because that's just how society has trained us to think. All that assuming the worst does is ruin relationships. Why? Because you convince yourself that you cannot trust that other person and what's a relationship without trust? A broken one.

Believe the best about others. Believe the best about yourself.
--J.