Writing is kind of like acting, in that you have to put yourself into the right headspace to do it well, You tell an actor to play a scene where he's really angry, and even if he isn't, you yell, "ACTION" and he's yelling and carrying on, then the scene ends and he's back to normal.
You seem to be saying your writing skill is best when you're in that depressive state, so you have to do what the actor does: Make yourself depressed just long enough to write, then get out again. An actor does it by remembering something in their lives that's like what the character is feeling, and feeds from it. It should be enough for you just to remember the feelings you once had. Remembering when you were depressed isn't the same as BEING depressed, but it should be enough to get you in the right place to write.
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Everything would be better if you were in charge.