Clutter is a reminder of things that should be getting done, but aren't, and can help fuel feelings of failure.

Laughter increases dopamine in our brains, which is a chemical that elevates mood. 

When you stimulate the pressure receptors in the skin, you lower stress hormones. Touching others stimulates oxytocin, which also has positive effects on our mood. 

Reflect on three things that are going well or three positive moments in your day, and even replay them in your mind.

There are actually some advantages to venting about a problem to a friend, and helping with your mood is one of them. 

Even mild exercise, about 40 percent of your max heart rate, can lift your mood.  Do activities that match your mood instead of trying to force yourself to do something you're just not feeling.