Feeling down can happen for entirely different reasons. Sometimes you can think your way out. In early recovery, I had what I called "funks", periods of being on the "pity pot." I invented something that worked for me. Rather than trying to avoid the episodes, I would allow myself to fully embrace them, but for a specified time. It could be for a whole day, or I might decide to let myself wallow without reservation for two hours or whatever. I don't think I ever used up my allotted time. I seemed to get over it after a bit of whining and self pity.
If you have been drinking to self medicate, it might be a chemical imbalance, and you may need to talk to a doctor about that. Let him know about your drinking history, and he may decide to prescribe something that will help. My ex went through a long depression after a period of cancer, which she survived, but was left with a depression that she could not shake. She went on medications, and I asked her how long she would be on the medications. She answered, "I don't care. I've never felt this good before."
In retrospect, I now believe it was something she had been suffering from for most of her life. There were some vague clues that I could not explain during our marriage, but an ongoing depression would explain it quite well. Like alcoholism, chemical depression is more about just being dealt a bad hand. It's not something to feel guilty about. It just needs to be fixed.
But try my trick about allowing yourself to wallow in your misery with a short time limit. It worked well for me. Maybe it will help you too. My general rule, well one of them, anyway, is not to run from your emotions. Experience them fully, but then move on.