It helps if you have a first party controller.When I transitioned from pro Brawl to semi-pro Melee, I had to understand that although I was near the top of the game in Brawl, Melee is literally infinitely deep in its gameplay. I started chatting it up with the world's best Smashers,and tuned in to their Twitch channels. If you think you're good, and you talk with people who are good, and try new things occasionally, then as long aa you fight people regularly, you'll be better every day.
Also, I fought CPUs for years. The day I actually played a real person, even though he was a terrible player, I got waaay better.