SO TRUE! But be careful what you think about. Here's a suggestion: "Finally, brothers and sisters, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworth
I took a class on positive psychology and many of these are backed up by research i've read. Also studies show keeping a journal is helpful particularly when we write the negatives down, something in the process of writing helps many people let go of what has bothered them.