You should distinguish between “accomplishing one big thing after lots of work” (like writing HPMoR) and “accomplishing one tenth of similar goals after lots of work” (like having some kind of applications approved). The first is hard and usually just not something people find they must do. I think that’s part of the problem. If everyone else gets by without writing HPMoR, surely I can. The second is annoying, but you can have a drink and forget about needing to be motivated and just keep at it.
For me, it would be hard even if I believed it necessary etc., because I cannot work alone (I tried). What I do must matter to someone “now”, and in a very specific way. Cheering me only made me feel uncomfortable, even if it was deserved. People cheer you on when they want something from you, not just when they are happy for your sake, so after you hear the ‘good job’ part you wait for the other shoe to drop. Someone finding small bugs in what I do helps much more.
(read the title, thought it was something like “you know you can do better, so if there are obviously novel challenges, just replace yourself with the better version of yourself and don’t fuss :) )