Think of your rehab exercises as having an equivalent impact on your body as depositing $$ does for your bank account - If you stop making deposits and just keep withdrawing, you'll run out of dosh -> grumpy. Similarly, if you stop the rehab exercises.... (but you know this!)
Yeah, I know. Turns out there is a downside to not being in constant pain. who would have thought!
A couple of days without exercises have had the predicted effect and I'm now re-motivated!