The thing is, our brain concentrates automatically on negative side of things. It is logical in a way, because it forces us to look for solutions. However too much may lead to depression.
Good news is that you can train your brain to see the positive side of things.
When I was depressed some years ago, I was only seeing negative everywhere. I went to psychologists, didn't help.
In the lowest point of my depression (crying all day long), I decided to force myself to find something that really made me happy everyday, every single day (a flower, the sun, a smile, whatever). I was writing it in an agenda. It was extremely hard at the beginning. And little by little I was finding nice things easier, I also started to look for those little nice things, I eventually started to create them. (the depression ran away)