Years of reflection and habitual modification
My biggest advice is ''work with it, not against it''
If you can find good reasons to do what you need to do, good reasons to avoid not doing it, ones that are actually compelling to you, to make not doing it way more of a hassle and way harder than doing it, then you're massively more likely to do it, and quite quickly
there was a point where i realised that all i do by not doing my class work and other such things is make myself have to do tonnes of it, hours on end, right befor e the deadline, feel awful the whole time i'm not doing it, just overall making it way more difficult, take longer, take more time in one go, and often messing up my work or my sleep, it was just so much more punishment and so much less efficient than doing it from the get go. it's not like i could get out of it. it's either i do that work or i end up flunking school and not able to pursue university and so on - which might be the choice you want to make (and is indeed the choice i ended up making when they kept locking work during covid, which, weirdly enough, was the worst and best time i've ever had with school)
one simple trick was to just give myself the gentlest start. every day, if i had stuff i needed to do, i'd just give it five minutes. if i still want to play games, talk to someone, go outside, read a book, whatever, i'd just do that instead. if i wasn't minding it, i'd just keep going. sometimes your brain just isn't working for a given subject.
the more and more annoying, the more and more terracore daunting it is to begin something, the less likely you are to do it. if you give yourself a no pressure attempt at it, it's almost without any possible consequence.