Sometimes it is difficult to tell when you’re making progress. Staying busy is not always a good indicator. Also, burning yourself out isn’t a good strategy. I think that a good metric is enjoying what you’re doing, or at least do something so that you can enjoy doing something else in the future.

I believe you have got to always ask yourself:

Am I making progress or I am I just stuck in repetition?

while(true):
  keep doing this for ever
  until god pulls the plug