There is work that is unpleasant but needs to be done (chasing raceconditions, memory leaks, etc.) - and there is grind, that kills all your love for the project. If it is the latter, I really do recommend to make a break and do something else. I tried both and grinding did not work out, but coming back fresh did and I usually immmediately spotted the problem, I otherwise would have wasted lots of energy on it.