Even after I became aware that I have ADHD in my 40s, additional years were still wasted after not getting treatment, with lost jobs, money etc. Sitting on a referral from the GP for 18 months now, and they don’t even give me an appointment in a distant future. The only thing that worked for me in my 20s: Set the bar low enough. Stop “planning” to study for 3 hours “tomorrow”, or half-assing 2 hours while a video plays, you are on the phone and get coffee 5 times. Instead, admit that you’ll only get 25 minutes in. But do them today, completely focussed, no distractions, not even getting water, no toilet break etc. Think of it like squid game. The team that gets the best test score after 25 minutes studying lives. You’d rather pee in your pants than to get up and certainly wouldn’t check your phone. Worked for me, can’t say if it will for you.