@improving2 figure out what's bothering you and then sort it out. If it's too overwhelming take a break and do something that makes you happy like taking a walk or listening to your favorite music, etc.
@Improving2 hope you're feeling better today! Would you remember what has made you feel better in the past? It's understandable to feel down, and sometimes we don't even know why. In some cases we do, but we don't know how to get past it. We all get through it our own ways. Distraction helps and letting it sting less with time is almost always a given.
@Improving2 as someone said, try to figure out what is bothering you and also why. Then try to see what you can do about it, ask for help if necessary. But i also find doing something i like of very good help (watching a movie, calling a friend, ordering food i like)