Remember, it's not a race!
Keep in mind that each person learns at varying speeds, some are quick learners while others take time to progress. Don't be ashamed if you feel you're progressing slower than your classmates. Remember the story of the tortoise and the hare? Keep that in mind when you're having self-doubts. The best musicians reached their level of success through determination and patience. It is not about how quickly you learned to play a music piece; it is about playing from your heart.
(Resource from the web)