I take Vyvanse for ADHD, but I also use tricks like the Pomodoro Technique, in which you work for 25 minutes and then take short breaks of 5 minutes or so. I have found that this helps me focus and also prevents burnout. In addition, it usually helps me if I have some kind of calming background music playing while I work, so sometimes I'll listen to DJ sets or something similar. I also find that if I work on the same assignment for too long, I become unfocused, so I will alternate between different tasks/assignments throughout the day at different intervals.

One thing that has not worked as well was being too detailed in my planning, because my brain seems to like flexibility. I had had a therapist who would have me write out a schedule for almost every minute of the day, and it seemed that my brain found that to be too rigid. So I use a modified version of that now, where it is planned to a degree but things are able to be changed if necessary.