[zwerdlds]

My suggestion to you is going to sound pithy, but its what worked for me: do problems. Lots and lots of problems.

Pick a direction (maybe discrete math, if you're trying to do CS) and get a book (I like EPP, as it is super accessible) and go, in order, through each chapter. Read, do the example problems, and do EVERY SINGLE PROBLEM in the (sub)chapter section enders.

Its a time commitment, but if you really want to learn it, this is one way to do so. IMO finding the right textbook is key.