I was diagnosed witu depression as a teen in 1989 with a further diagnosis of PTSD some years later. I have been given all the meds and have seen multiple therapists over the years. Nothing works. Nothing "fixes it". The only effective course of action (for me) has been persistence.
For two years (~2011) it inexplicably went away. Just to fuck with me and remind me what being alive actually feels like before slowly sinking back into the mud. I have been off meds since 2018, after the misery almost killed me (heart failure). I beat it, and by the time COVID and cancer (2022) showed up, they didn't phase me.
So, my only piece of advice is, persist. Remind yourself of the things that are good in your life and focus on what you have control over. Focus on what you have not what you feel you should have. All the guilt and desire over how you should feel or how it should be, is going to do is make you proper miserable and probably make you miss out on a few good windows. IMHO
PS: Just because I learned to cooe without meds does not mean it's the right thing to do for anyone reading this. Consult your medical professional before messing with your medications in any way (obviously).