Cheering up is a matter of taking one small step at a time. Make that first step a healthy snack. Some favorites of mine are:
Don't wolf down your snack. Savor it. Breath in the aromas. Take a bite or drink and hold it briefly in your mouth, tasting the flavors. Notice that your spirits rise with each bite or drink.
There are more cheering up articles under Mind and Attitude in the index.