One of the problems I experienced trying to hold motivation was a sense of futility. There really isn't a sense of progress if you're just aimlessly solving problems with some abstract notion of getting better. Instead what I found helped is trying to work towards some sort of goal, for me that goal was to improve my _approach_ to leetcode problems, not necessarily focus on how many I can solve.
Through this I found out that most leetcode-style problems fall into one of a number of solution 'buckets,' and the challenge shifted more into a problem classification task, rather than a coding task. I found my ability to do (a very few) hards unaided its own reward and motivation to continue! Up to a point of course, at some point it does just become repetitive again. This website helped a bunch: