I would also recommend yoga or another sport with less impact, something you can do at home or before riding. Just so you avoid any major injuries or spasms :) hope it helps!
A healthy diet and enough sleep is probably the biggest factors.
You're probably getting enough excersise just from the job.
I take supplements and other vitamins to help with my "issues" to be able to keep going all day, if I slack off my diet I need to nap during the day.
I ride 4-6 horses a day and care for 30. As well as other farm tasks.