Though I know you have already been told, I am going to say it again, never feel guilty for needing time. When my mom was in the middle of treatment I made sure my dad had "time off" I figured, even though I went to every appointment and was at their home everyday, I got to go home at night. It was also good for my mom, to have some time away.
That is no reflection on commitment or love, it is necessary.
You recharge those batteries!!!
Prayers to you,
Dana