The motto of alcoholics anonymous is "one day at a time" and that is a great way, also, of dealing with feelings of sadness. Sometimes we just need to do one thing. That is a way to take the first step on the way to feeling better most of the time. So today, choose one of these things and do it, or do them all.
Make your bed. This has surprising mental health benefits. It's kind of amazing really.
Help someone else. One very simple way to start is to visit The Animal Rescue Site and click to give food to shelter animals. Don't stick around and read any stories about animals that have been mistreated, but you can watch the Cute Dispute as much as you want.
Do a random act of kindness. My favorite and a very inexpensive one is to put quarters on top of or in the gumball machines at the grocery store. :-)
Call a friend (actually talk, not text.)
Do one of these today. I only included 4 today because I don't want you to get overwhelmed. Just do one. The smallest thing can make a huge difference in your attitude and your feelings.