Falling behind physically ? Yes always struggled with it being without half a lung . injurys may have some bearing on the lack of motivation i just now can sleep on my shoulder from a tear in the rotary cuff.(aikido) and a persistent quad injury so that can be a factor.
Your original post didn't mention injuries. That's kind of a different issue than general training angst.
If you're injured, rest. Go to the dojo and watch class if you want, but stay off the mat until you're better.