Actually the part where you make a breakthrough and find joy again is when you stop doing things you feel are wastes of time and do those harder, more complicated things that you feel aren’t.
I tend to think as a rule of thumb that making things feels so much better than consuming them. Consumption is wonderful and there’s so much to consume today, but to make something of your own has a kind of fulfillment you just don’t get from other endeavors.
Build something, make something, write something. Just go write a shitty scif-fi novel; you’ll surprise yourself with how good your “bad writing” really is. Go start composing music, or learn programming, contribute to Wikipedia or some other public repository and get involved with them. Do something flagrantly and deliberately creative but non-productive, i.e., not work, no expectation of renumeration, not a job.
You’re probably thinking, well, i don’t want to do anything. But i’d bet that’s not entirely true. Think back from before you felt this way, remember some aspirations you used to have, those half-baked ideas you set aside years ago that you never worked on or set aside because i have to be Practical and Responsible, and just … start one of them. I mean don’t ‘start the process’ of starting, just frelling buy/bake/write/compose do whatever it is, as imperfectly as you do it. What the hell. Want to own a bake shop? Hell, you’re an adult, go rent the damn space and start getting equipment to bakerize it up. Get a loan for 50k-500k and start a fun side business; why not? I mean, what can you lose, right? You already feel bad and the heat death of the universe is going to erase everything eventually anyway. Just try it! Just breaking routine for a few days feels like a whole new world is possible again.
Another thing to remember is all the successful people who are much, much older than you, still plugging along and creating and making and doing and being handsome/athletic/successful whatever. It’s not the end. It might be a bit harder, more deliberate, but it’s still possible!