Sometimes it is not about being "坚持". This is not a race, where if you stay in there long enough, you are bound to complete. If you find you've reached a 瓶颈, it may be a good idea to take a break, and come back with a fresh perspective.
It is easy to complete 500-1000 words, but not so easy to write the right words. 坚持 sometimes doesn't help, because you aren't looking at the issue with fresh eyes.