High protein diet and regular physical exercises are important for a good stamina. Start by exercising a little bit at a time, and gradually improve for more each day. Follow a healthy diet of proteins and minerals. If you are regular in your diet and exercise, you will grow stronger and improve your stamina. Try doing 15 minutes at first, then every day increase enough by gradual increments so that you start to feel refreshing as you go on. Jogging or swimming are good exercises to help with this.
Take care in gradually practicing more faster and repetitive reps instead of slower and heavier reps.