I don't think you can count 'rejected by YC' as a 'negative experience'. It's pretty much the definition of 'non-experience'. It's like saying that the department store experience was bad because they wouldn't sell you a lawnmower at half price when you asked them to.
I was rejected by YC a couple years ago, and I mostly enjoyed it (I loved talking to the AppJet guys).
The fact that I didn't build the company I was pitching is prima facie evidence that I agreed with their assessment. (and in retrospect, I wasn't the right person to do that company and you could hear it in my voice)
That's how I'm viewing it. If I get rejected, that should be motivation to build the company I want and prove them wrong. The odds of being selected are low. That shouldn't be considered a test of you or your idea.
