Untwist your waist!

When you do this exercise you are working with the muscles that rotate your trunk at the same time as curling you up into a ball. If you have tension here, you may be twisted slightly to one side.

Removing this twist may well help you to feel much more comfortable! Straightening your posture will also make it easier for your horse to work symmetrically; problems such as throwing a shoulder in, or out, difficulty with maintaining a straight line, or difficulty with one particular bend might be improved.