Id like to think of the brain as a muscle. The more you use it the stronger it gets until a certain limit and vice versa. Say Ive been a neet since highschool ended which is about 2 years ago and only very very recently dedicated time of the day to study early highschool math.
Following that train of thought, how much brain power have I approxomately lost and how many days of continous study will it take to surpass my old self? How many days of continous study will it take until my brain is used to studying several hours per day? How many days of continous study will it take until I have mastered highschool math?