I'm a soldier. I fight in a war(no literally), and I have to prepare myself for the worst.
1.- Prepare my weapons. Hard commands and complicate combos have to be learned and practice so my body remember all better than my brain.
2.- Know the opponent. Try to fight as much as possible against all characters, even rock tier level. Check setups, combos, frame data, specific character player habits (like 6BBB of Amy's users) and recreate possible scenarios and options.
3.- Build Stamina. A good athlete have to give the 120% all the time; in big tournaments you have to keep going and going with short rest sessions. Be ready for it. Endurance is the key.
4.- Concentration and Reaction. Its common to hate turtle's gameplay, but in some random moments you have to rely in all your patience to wait for the right time to attack. Rushing to attack all the time make's you predictable.
5.- Watch and learn. You don't know everything. Even from novice players you can have a good lesson. Try to watch as many videos as you can. Maybe you can find really easy answers to old and new problems.
PD: If everything I wrote before doesn't work then you need a special training called "OMEGA's Training"; maybe you will know why Dominican's players name it like that.