If you want to be successful at anything in life, it is important you have a certain level of confidence. You must have confidence in yourself, in your ability, and your preparation. And please note there is a fine line between confidence and being cocky or arrogant. Confidence is crucial to success, cockiness and arrogance can ruin success. Ask any of the best players and they will agree. The best players in the world have a confident swagger about them. They know they can play because they have put in the work.
Confidence is especially critical when it comes to shooting the basketball. If you don't think the ball is going in every time you shoot, then why are you shooting? Ask any good shooter and they will tell you the "next shot is going in." They will tell you this even if they missed their last 10 shots.
How do you get confidence on the court? You prepare. You strength train and condition so fatigue is never a factor. You spend hours a day shooting hundreds of shots. But you don't just go out and shoot; you take game shots, from game spots, at game speed.
"You only feel pressure when you are not prepared."
If you are ever in a shooting slump, go back to the basics, and put in the work. Most shooting slumps are mental; they require a check up from the neck up. If you put in the work on a daily basis, you have to believe in yourself that it will pay off.