A lot of people are depressed because they're fixated on the negativity. You'd be surprised how much going outside, exercising, or even just doing simple things like taking a nice cold shower or cleaning up your room can help.
Obviously it'll be different from person to person but generally, setting a small goal and accomplishing that goal will make you feel better.
And some like me prefer a long hot bath. That feeling of being a part of the primordeal soup once again, cutting the middle-monke. Can't have any complex problems if you are a mere microorganism. That's liberating. Shower is clever, operational, you can take it fast, frequent times a day if you need so, but it's these moments I know I'd never have a shower stall in spite of it's practicality and size. Bonus points on finishing it with a colder shower to assemble oneself once again.
"You see this? This is you. I'm serious! Right here, life is about to form on this planet for the very first time. A group of amino acids are about to combine to form the first protein. The building blocks...of what you call 'life'. Strange, isn't it? Everything you know, your entire civilization,
thinking about it, isn't Q telling a lie here (and I'm shocked, SHOCKED. I never expected Q to LIE)? Isn't it canon that all humanoids stem from the Progenitors?
Never thought about that one. They just said that they seeded planets with their DNA, so I would think they could have done so after this happened. Simple life arose, then they guided its evolution by providing genetic material.
Even just setting aside time to express gratitude can really turn things around. I have my kids do this, and that alone can turn them from being hugely negative to happily going to bed more-or-less on time.
It obviously can't cure all forms of depression, but recognizing things that you're grateful for can really improve your general outlook. It's the indoor version of touching grass.