I've been there - having a job which doesn't takes up all your energy, and you're left with nothing for other projects such as blogging or design or anything else.
I think the best thing you can do is to not beat yourself up too much about it. I managed to get back into writing, at least for now, by only writing things I like writing, and only when I actually feel like it.
I tried to make an obligation out of writing while I was still at my last job and it was bad. It was much better for me to just do it as a hobby, once in a while, when I felt like writing.
Just keep taking care of yourself and do everything else when you feel comfortable doing it! :)
Yes, definitely better to not force it. It just feels... unfair if you're left without energy, just because of the job. It's hard to find a good balance. I do want to write again, but like you say, only when I feel like it.
I did manage to keep up with designing once in a while, but only when inspiration hit. That wasn't often, but atleast it was something :-)