The urge is always there - I'm a better artist now than I was a year ago, when I started my comic, and I'm going to be a better artist a year from now. And that is always going to be the case. I'm always going to be improving.
I've decided that aside from corrections of obvious mistakes (like, stray ink-lines I forgot to erase, instances where I missed colouring someone's eyes, or moving a confusingly placed speech-bubble) for print, I'm not going to go back and re-draw anything, because it's very likely that if I started doing that, I would never stop.
I'd get stuck in an endless loop of re-drawing old stuff, learning better, going back and re-drawing stuff that isn't up to scratch, learning better, etc. - and so on forever and ever.
The best advice I can give you is to stop re-drawing stuff and start moving forward. It's okay if your first pages aren't perfect. It's okay if your new pages aren't perfect. It happens to everyone - including professional artists who have worked for decades.
Let go and move on.