A once a week schedule requires that you only miss your lesson when absolutely necessary. Missing lessons is a principal cause of problems for many adult riders. Everyone is busy and there are many demands on time what with work and parenting responsibilities. Be sure to schedule your lessons at your most convenient time and if you foresee problems check on the instructor's make-up policy. When the student is a young person, it is up to the parent to prevent over scheduling.
Riding is an athletic discipline and is such is more easily learned by the young.
If you are not a child you will find it helpful to do some stretching before each lesson. Stretches that emphasize the legs, inner and outer thighs, front of thighs, buttocks and back. Be sure to check with your doctor before beginning any new exercise regime. Your instructor should begin each lesson with some appropriate stretches but you will still benefit by doing some on your own before you mount up. When in class, be attentive and if you do not understand something ask that it be explained further.