I really love computer science, coding and mostly all the amazing things you can do with this knowledge, i feel i finally landed in my world.
I'm doing a Javascript course now and while it is really engaging to learn about how a language like that works and how to build with it, i'm getting quite tired and frustrated..
Now, i'd say i am quite meticulous when studying and i use some studying techniques to really integrate what i'm learning, but that means that 1h or even less lesson can take me all the time i have to study in a day to be understood, noted down and then repeated over the following days..
There are a lot of quite complicated concepts to understand and memorize, and, as i'm also working, sometimes it gets quite tiring.
I feel like there's this huge amount of never ending work and concepts before i can actually start do something cool with the knowledge i have, and i really want to start doing something cool.
I re-started to study after many years so i'd say it's also because of that if i'm not really used to it and i can't process much informations at the time.
How can you get better into gaining knowledge? how can you prevent getting fatigued?
I definitely recommend either working on your own project (as others have suggested), or also just try modifying an existing project.
If you're into Video Games, there's a great FOSS project called RomM which is basically a game manager website for roms. You could try to run the project locally, dig into the code, and add a new text field onto the site (maybe a link to HowLongToBeat?) From there, you could even tackle one of the issues. https://github.com/zurdi15/romm
Obviously it could be any project that you are passionate about, but the point is that sometimes it's better to understand someone else's code base before doing something from scratch. Plus that's a skill you will need to have when working as a JS developer.