If you can do any sort of physical exercise, even if it's taking a long walk, that's been known to release endorphins to help a little bit.

Consciously controlling your breathing throughout the day in sort of a meditative manner can also be calming. You can do this a few times a day, or whenever you need.

If you need to vent, or talk about your feelings, I am confident that there are people here who can relate to your feelings and possibly be able to share their lessons learned / helpful experiences. There may even be a #depression tag? But if you find yourself falling deeper into a black hole feeling while reading or watching content there, please stop and look at something like #happy or #motivation or anything up-beat that makes you feel better! :)