Generally speaking, educating yourself about the mechanisms of depression (and/or anxiety, ptsd, any other problem you could have) helps a lot. Like - what kind of thoughts it gets you into, and how it sometimes lies to you about things being worse than they are. "Know your enemy", I guess, at least that's what helped me.
If you haven't done it in a long time, get blood work done, since some physical health problems might worsen depression. They are rarely its only cause, I'M SAYING THIS BECAUSE I KNOW THERE ARE PEOPLE WHO SAY DEPRESSION IS *ONLY* A RESULT OF VITAMIN DEFICIENCY OR STH AND I'M NOT ONE OF THESE PEOPLE. Anyway when I saw a psychiatrist for my mental problems he also suggested me to do blood work, in my case some deficiencies worsened symptoms like tiredness and stuff. Not much really, but still something.
The resources thread linked above can be very helpful. There's lots of free therapy worksheets/resources online in general, I haven't looked much into it myself but I'm pretty sure that if you google "free CBT resources" or "free DBT resources" or just a variation with any other therapy approach (because there are quite a few as you may know already, and all of them work a bit differently) - you will find some things.
If you have anyone in your life who you can hang out with, talk to, anything - any friends, family members whom you have good relationship with, even a pet - spend time with them, don't isolate yourself. Of course, I'm talking about people that you feel comfortable with and that actually make you feel better. Yes, I know this is obvious advice, but many depressed people tend to isolate from everyone and it worsens their situation.
Try going outside, don't spend all of your time at home. The thing is, when someone's feeling bad and stuck in the same physical location it's also difficult to move on mentally, so sometimes going somewhere, just anywhere else might help you a bit.
"fake it till you make it" doesn't work long term, really. So I'm glad you're not choosing that. It can make you feel better for some time but then you will crash, terribly, and it's just not worth it. Try to be honest with yourself, think about what things and activities make you feel better, and what makes you feel worse. Keep in mind, everyone's different and needs a different approach in recovery. Just because things that "work for most people" didn't work for you, doesn't mean that there's no hope, you just need to try something else.
Also if you have the option to try antidepressant medication, consider it. For some people it changes the game a lot, really, and it's much cheaper than going to talk therapy. I know many are reluctant towards it because of the side effects, but it's still an option to think about (for me, personally, meds helped a lot, I was quite lucky with that one thing). I don't know if you have access to this option though.
I assume you might have done some of these things already. Much of this is very classic advice and you might be sick of hearing it once again, but idk, maybe something will help, if not, sorry.
Good luck! I hope you can find something that works for you. The fact that you want to get better is a lot already.
