We got a rejection letter this morning. Definitely not going to quit. We hit a quarter million in our first year, cracked a tough technical problem, and are significantly growing end-user usage every week. We got one video view, so it's prompted to me to dial back the confidence and write a list of all the reasons our application was thrown out and that process has been very helpful.
Also, remember YC has open sourced a ton of its knowledge (Startup School, Stanford Course, PG essays, Sam Altman Playbook), so if you read a bit every week you have their guidance for free. And maybe you'll be better prepared for a Series A 9 months from now after getting into the next batch. Life's about good timing.