I think its fair to say that YC only wants founders and businesses that will succeed without YC. With thousands of applications, hundreds of invites and tens of acceptances they can’t invite everyone. Not getting an invite does not mean you won’t succeed, anymore than getting an invite means you will.
For those that are soul searching, ask yourself a few questions.
Is our team credible; can we really execute? Do we have enough people with the right skills. Engineers are just more appropriate than english majors.
Will we see the project through… there will be lots of rough spots, will we give up?
If no, fix the problem and apply again.
Am I more than one founder? Solo founders are a risk. Something happens and YC’s effort and money is wasted. But probably more important, being a team is an effort multiplier and a barrier against stupid mistakes.
Find a cofounder or realize that you are probably not right for YC.
Is our idea unique? If yes, is it really something people want? If no, is it sufficiently better than what's out there. 10X improvement?
If you don’t have a good idea, get one.
So you have a good idea and you can build it. Can you get users? Where is the evidence? Passion for your project can blind reason.
Can it make money?
There are plenty of companies out there that are perfectly viable who received rejections. Who knows why - you didn't fit the YC mold, you didn't submit your application early enough, you’re a solo founder, you were too busy programming to correct your grammar mistakes…
if you were rejected because you can’t execute, have a bad idea, can’t get users or won’t make money, then you should really rethink your startup.
We built, we launched, we hustled and we grew. 12 months ago we launched a nationwide TV campaign. OpenRent[1] is now the largest letting agent in the UK (bigger than Foxtons for example), established, and well on the way to fully disrupting one of the oldest industries in the world.
YC rejection was tough, but we believed in the idea and whilst I'm sure YC could have helped us make fewer mistakes, it didn't stop us wanting to solve the problem we all believed in. So we went and did what it took to succeed.
Chin up to anyone facing rejection - use the information learnt from the application process, and go prove them wrong!
[1] - https://www.openrent.co.uk