Ditto what everyone else said, and you just do whatever you can to care for yourself as well as mil and DH. It doesn't have to be cycling, though if you ever can work up the energy for a ride, you may find that it does wonders for your outlook. DH and I have been primary caregivers for both my mom and my dad, at different times, and we found that you have to work just as hard at finding ways to "decompress" yourself as at caregiving. Don't forget to take care of you.

Hoping for a speedy recovery for your mil, and hugs to you.