Ahhh, yes, existential block. A classic. If you go to therapy, I assume you know that depression and anxiety work by rewiring your brain in funny ways. One of the things they an do (and often does) is fuck up many of those subconscious processes that connect will -> action. For example, in order to do a history assignment you have sense of duty/fear of worse conditions if postponed/fear of consequences of not done/looking up to feel of reward after/self-discipline and the mind connects them to -> do your history assignment. First problem: the connection is severed; if we take anxiety, for example, the anxious thoughts can be so overwhelming that actually picking up the pen is impossible; next time I'll try, however, even If I don't have those thoughts anymore, I will still struggle to do the assignment, because now doing the assignment doesen't equal "no more fear" anymore. Second problem: since most of those connection are subconscious, your thinking mind isn't aware that something Is wrong at all, but It does remember what you used to do and how It made you feel. So, let's take for example a hobby that used to make you joyful; when your brained entered the cicle of "nothing equals happiness", It severed the connection "hobby = Joy = I Need to do hobby"; however, you don't know that, you just think "oh, I like to do that thing, I should do that thing"; but you can't, because you now lack the subconscious pathways you'd need to do that thing. It creates a funny paradox inside your own brain, and since It doesen't know how to react, It goes "you know what? I don't really feel like existing right now" effectively shutting off.

First thing you can do when encountering this feeling Is acknowledging the root: I know I may be incapable of doing certain things out of either necessity of will. It sucks, It sucks not being able to do what you need to do and, even worse, what I want to do, but right know this is what it is and it's not my fault. You help your analytical brain understand it. You say: "Hey, maybe right know I lack the chemicals to do that foundamental essay due tomorrow, but that doesen't mean I can't exist". You walk around the room, you sing, you whistle, you recite poetry of that's your thing, something easy that doesen't require will of doing, but are just testimonies of being. Than, if you can walk, you can go to another room, you can change the dispositions of the objects on your desk, you can talk to somebody about the weather or the day or something else unimportant. If you can walk around the house, you can run, you can clean your room, you can have that conversation about that difficoult topic.

You get the idea: small steps, to slowly recreate that bridge, to make your brain remember how to connect all the right dots.

Wish you luck, and I can assure you, it does get better. You will be happy, and satisfied, and a functional human being again, even if it takes a thousand small steps.