Don’t worry, this happens to a ton of players.
Stick to a few characters. You’re actually better than most of the scene at this, as you play more than three characters. This is good as the best players can juggle 5 characters, but stick to 4-6 characters and learn them. F Champ has Phoenix, Dorm, Doom, Magneto, Combofiend has Dante, Spencer, Hawkeye, She-Hulk, Taskmaster and Nova and Chris G has Morrigan, Doom, Akuma and Ryu. By learning more characters, you get more options and it keeps you random as a competitor(Despite what some say, random is good). Just remember to LEARN the characters, don’t dabble in them and think you know their gameplay, take time out of your day to study these characters. The more you do it, the more you grow.
Have an overall sense of what your game plan is as player. Are you rush down or keepway? Do you want a strong point, a strong anchor? These variables need to be settled for you to create the perfect team.
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Read the guide and apply its information to your problems. Remember to never give up and keep playing.