This took me way too long to figure out. I'll be twenty by the end of this year - my year group will go on to their second year of university this September, if they've succeeded so far. Meanwhile, by these measurements, I've got nothing. I've failed three years of A levels, although some of this can be blamed on my mental state being iffy for some time after failing the first year. It's a question of what are you willing to sacrifice and what are you willing to struggle through.
Despite all these vast differences in our lives, we're all united by the biological limit of 24 hours per day. No matter how poor or privileged you are, that is the truth. Privileged people just have the means to maximize the value from this to their advantage. E.g. if you go to a good school with good teachers and leave with great grades compared to someone from a poor school who got average grades, you've derived far more value per time spent over the years there. It seems that over the past three years I prioritized bad sleeping patterns, reddit, music, movies, books, games, politics, common chatter, and just hanging out. It took me until now to realize that it was wrong to do so with some of these - that there's little return of value per time spent on things, especially past a certain point when you consider diminishing returns. I don't think I needed to listen to hours of music or mindlessly surf reddit before going to bed at 2am - thirty minutes of each would cover most of what I needed, so to say, but here we are, that's what I chose to do.
For practical advice, all I can say is keep a consistent sleeping schedule - make a google drive document or something where you write down the hours you go to bed and keep consistency - if you go too late to bed, try to reduce each time by 5 minutes per day until you get to your goal.
Choose to struggle through the things that have the most return first and as early as possible in the morning. Do homework, revision, gym, do these in the morning if possible. Social life is very important but most of that is based in the evenings and at night. Most of the time spent socializing in lessons or at work is just there to waste the time - if you're not hanging out by choice in the evenings and at nights, you're not friends. Don't spend time on what are temporary friends by convenience of simply being there.