Comment by hackermailman

If you can't concentrate then you don't know why you are doing it. You have to write down what overall goal you want that you are very interested in then break that up into weekly research tasks where now you recognize that doing those tasks is necessary for said goal.

The only time I really used leetcode was to practice a basic linear algebra course. I had the idea to identify every non-linear problem on leetcode then see if I could use the course I was doing to practice writing linear approximations as solutions then leetcode was interesting to me otherwise yeah I can't just sit there and do it hours per day without a reason either.

Try briefly auditing some advanced open courses and see if anything there is interesting to you that now require self-directed research so you can figure out what's going on. Erik Demaine has a bunch online.

Find an open source project that is interesting and become a contributor now you have to teach yourself the codebase and whatever it is they're doing. Find a technical podcast then make a YouTube video animating in some software visuals to describe what they're talking about. Whatever you choose it should be something you really want to do everyday and then discipline isn't a problem