To me, it's more or less trying to find ways to improve my previous art style. I never redraw old portraits or comics because they're a part of the "evolution" process.
Powering through is an option, yes, but I don't think it necessarily improves anything. When I feel like I'm in a slump or my art is lacking, I find different ways to adjust my drawing style to add a bit more flair/more detail.
I think this video by "Draw with Jazza" sort of touches upon that (though, not in the same context.). Try to break out of your normal boundaries and take inspiration from everything around you. More than likely, you'll see your art improve over time.
^_^ It's always fun to compare your new stuff to the old every now and then just to give yourself a confidence boost, too!