I can't speak for everyone, but in my experience, it isn't really even the idea of a grind, even a big grind, that makes it hard to continue- it's random % chance drops. If you have a big list but you accomplish it a little bit at a time, it still feels like progress. If, however, you go an hour or two without making any visible progress at all, it's a huge hit to morale and makes you feel like you could be doing virtually anything else.