Perform as much as you can, and in a variety of settings. Play solos - play duets - play in the marching band - play in a concert band - try some jazz - play in a brass quintet - don't restrict yourself to playing just one style or type of music. The more you expand your horizons the more you will grow as a musician. Get into an ensemble (or sit in with one) that has better players and learn from them.
Listen to a lot of trumpet music, decide who you want to sound like, and work to emulate their sound.
Strive to be a little bit better each day as a player - making incremental improvement. Don't feel like you need to become a superstar overnight. No one else ever has:)) I have been playing since the fifth grade which was in 1959, and I am still learning new things about music. I am writing this in spurts while resting during my daily trumpet practice.
Never be afraid to make a mistake. Everyone that has ever played a horn has gacked on a note.