Head for the light. The darkness is stronger and will try to pull you down.
Advance apologies, but, I must say it:
"Darkness has a hunger that's insatiable, and lightness has a call that's hard to hear."
And so it is. You have to work to find your happy place. I have drawn on many of the wisdoms of the ages, in times when the darkness is winning. Finding what works for me. NOT meds, except for a little responsible abuse of moderate adult substances, maybe?

The things that worked for me are, in no particular order, St. John's Wort (go figure?), EXERCISE, getting involved, helping someone or something, visiting or thinking about people who are worse off than I am, and generally THINKING positive, fake it till ya make it. All of the things that have always worked for people. The exercise piece is crucial and should ideally include beautiful places in nature you had to work to get to (hike, kayak, snowshoe). I have totally changed my mood and mind around by going out and beating my body to a pulp with activities.
Having gratitude for one's blessings. Having a humbling experience, getting yo ass kicked a little further down the Path of Enlightenment, and learning to let go of Ego.
Learn to play an instrument and lose yourself in practicing. Book a gig many months hence, so you have a date to work toward.
Music and theatre stuff keep me going, have a goal to work toward. The show must go on!
Good luck.