The same way we exercise our bodies we have to keep our minds healthy. We must train ourselves to get rid of the negative emotions and unpleasant experiences. Just let it go. Make room for positive thoughts!
So, it is really up to us to observe and train our brains, therefore our direct our thoughts in the correct direction – meditation, mindfulness helps us focus on what is important and relevant – leave all the bad stuff ( negative thoughts, negative people, voluntary and involuntary bad emotions, etc) as far away as possible…delete them really.
We tend to give our thoughts too much credit. Therefore we think our thoughts mean something, that they are real. We worry too much and that creates so many negative emotions. Thoughts are like leaves following down a tree in a changing season. You can’t stop them. What you can do is to let them go, let them just float by and just be an observer.