Take a day off
Mild depression often arises when people overwork themselves and get stressed out. If you find yourself in this situation, take a day off to do something else from your regular schedule. You can get your favourite lunch, head to your favourite spa, take a drive to a beautiful park or hangout, among others.
You can also hangout with your friends, but make sure these are people who are optimistic and have positive thoughts, as those are the attributes you need at that particular moment.