Something interesting I've learned about depression and cognition is that being depressed (if you're high functioning) teaches you how to act independently of motivation or emotion in a way.
Depression = anhedonia and a lack of feeling or constant negative feelings -> feeling like shit and never being happy makes me not want to do anything -> but I still have things I need/want to do -> I need something besides happiness/enthusiasm/desire/fun to motivate me into action.
The emotional pain is still there, but you're at least keeping your life together so that "I neglected my job/health/etc and now I have even more problems" doesn't add to the list of problems you're already experiencing. In other words, your new motivation to act isn't to make yourself happy (bc you can't force yourself into being happy) but to keep your head above water. Not getting worse becomes positive progress in itself.
Alternatively, if you're success-driven it can be kind of "fun" (however much it's possible to have fun with depression-induced anhedonia) to give yourself a game of "how functional and responsible can I be while still feeling like dogshit." Probably the one time I would recommend equating the amount you suffer with how successful you are, because in that case you're looking at it more as "wow look how much I accomplished despite my pain" rather than reveling in the pain itself.
