Poker is a mental sport. Training for a mental sport is similar to a physical sport. You break the game down into pieces and get repetitions in on those things.
In basketball you may practice free-throws for 30 minutes per day. In poker you can practice memorizing the correct raise-first-in ranges. You can practice playing against check/raises with something like Simple GTO Trainer.
In sports you’ll often watch film and break down areas for improvement. In poker you can record your online session or review a hand history and break down areas for improvement.
All sports have coaches. In poker you can hire a poker professional to give you feedback on how you can improve.
External things like getting enough sleep, eating a healthy diet, mediating, journaling–these things will often improve performance for both physical and mental athletes.