I just try to work on something different if something isn't working. Inspiration exist, but it has to find you working!
if I'm bored of drawing comics, I just draw random doodles
if I can't seem to write something or I can't concentrate, I focus on drawing comic pages
or I focus on doing patreon content, there's always something different for me to focus on.
I'm always kinda tired, but when nothing works and I feel absolutely disgusted by everything I just take a week of resting from the computer screens and try to play or go out... until I feel the urge again to resume working.

I'm not sure if I'm doing something good or bad with this, but I just take my comics and drawings as another job, so I force myself to work even if I don't want... I guess it helps that I don't take many commissions and most of the stuff I do are personal projects in my free time.