Been there; had a hip replaced about 7 years ago, spent a summer doing BC three years ago. Looking back, they are blips on the radar, but I remember both events being all-consuming at the time. Try to stay positive about the BC treatment. I was lucky, got by with a lumpectomy, but I did do both chemo and radiation. The supports for chemo, in terms of recovering your immune system and preventing nausea and related discomfort, are very good these days. It is not the horror that is often associated with it; I actually worked full time except for the week of infusions, when I missed the day of (Fridays for me) and the Mon and Tues following, half day on Wed. My infusions were three weeks apart. Yeah, you loose your hair, and that’s a hard thing to deal with, but your horse, and those who love you, don’t care ;). I actually told very few people I was going through it, and very few noticed the wigs. That said, how your body deals with chemo is very individual; hopefully, the fact that you are active and have horses to keep you going will stand you in good stead. Respect it, but don’t allow it to rob you of who you are.
I have my horses at home (two horses, two mini-donks, pasture w/ run-in situation), and I had a college student to help me the two or three days after each infusion that I felt really trashed. Otherwise, they were a reason to get up and move, which helps. Radiation was a lark after chemo. Take care of your skin, get a little extra rest, and the biggest inconvenience is taking a chunk out of your day to drive to the clinic, get zapped, and drive back to the office.
Good luck; feel free to PM if you want to talk or have questions.