Sounds like you set your expectations for yourself a bit too high. That's what ambitious people often do, and it's not a bad thing to have ambitions, but it leads to disappointment when things aren't going the way you planned. Try setting your expectations lower and you might surprise yourself more often. And I'm not talking only about art here, this applies to almost every aspect of life.
Just remember that we're all human beings, no matter how awesome or unique we might feel at times of success, we all have that moment of realization, that in the end, we're not all that special. Some might get depressed over that fact, but the fact that nothing matters and won't matter in the grand scheme of things makes enjoying our lives much easier without worrying too much.
Think about it like this: You have a limited amount of time on this earth. Unless you make some ground-breaking scientific discovery, not much you do will matter in the far future, so all you really have is how you will spend that time you have. Happiness is the only thing that really matters in the long run and all the time you spend in depression is, for a lack of a better word, wasted. Just view life as an equation of happiness and enjoy the small things that keep us going.
I know it doesn't work like "Get happy plz", but is it not worth a try to enjoy your life? If not for yourself, then for the people who care for you, for your friends and family, and the people subscribed to you, waiting for your next lewd art compilation (god I miss those

). It hurts to see a fellow artist suffer.
That being said, I'm sure you're tired of those anti-depression walls of text, so I'm just gonna say, just do whatever makes you happy in life, even if it means giving up on your art. While I (and many others, I'm sure) am gonna miss it, there is no point in doing something you do not enjoy anymore. Find another hobby perhaps, anything to take your mind off those heavy thoughts.
Wish you all the best mate! :]