The point is important so you think you can work through it. The pain worsens so you stop. Once you stop, the pain usually disappears. You have just experienced a side stitch.
The side stitch is caused by a muscle spasm of the diaphragm. When we inhale, air comes into the lungs and presses the diaphragm downward. When we exhale, the diaphragm moves upward. When you eat a big meal right before you play tennis or when air has gotten trapped below the diaphragm, a cramp (stitch) can occur.
How can you get past a side stitch? The best immediate action is to try to stretch out the cramping muscle. This can be done by alternating your breathing pattern. Take a deep breath in and hold it for a few seconds. Then force the air back out through puckered lips to restrict the air flow. Other professionals have mentioned that crouching down and stretching tall helps by flexing the abs.
Best way to avoid side stitches? Increase your fitness and conditioning training to strengthen your abdominal muscles. Make sure that you do not consume too much food or liquid prior to play because the added weight increases the downward pull, which can help to cause the stitch.