How long did it take you to get tolerant to your medication?
I went through a round of neurochemically-inspired regret for the things undone this year too. It's not true; it's just a figment of our mood-states. I've found it helpful to remind myself constantly that thoughts and feelings are transient; actions are what really count. So no matter what I feel like, I can still function in some capacity.
Besides, you're on HN, you must be doing something right.