I 100% relate to this. I have a full time job, 3 kids with one on the way and a small farm my wife and I are trying to build up. By the end of the day all I want to do is go to bed and watch TV. My energy is completely sapped.
I fail a lot of nights to get anything done but I have found one trick that seems to work pretty well and that is committing to 5 minutes no matter what. I put in 5 minutes of illustration work no matter how tired or uninspired I feel. Sometimes 5 minutes is all I can squeeze out but at least I kept the fire burning so to speak and I'm 5 minutes closer to a finished project. Often though, five minutes leads to an hour or more and I notice that I forget about the exhaustion or stress of the day.
You also might be able to apply that to 5 minutes in the morning before work or at a lunch break. Anything that keeps you moving because I've found that when I let a project sit for too long it gets harder and harder to get back into it.
Anyway, I don't know if that helps but keep at it and don't put too much pressure on yourself.