Thankfully, when I was inexperienced, I've never decided to blame myself if a girl couldn't have an orgasm.
As I built more experience through the years, I realized FOR CERTAIN that if a girl couldn't orgasm - that it wasn't MY FAULT.
Certainly there's been times that my performance lacked for one reason or another (drugs/alcohol, lack of sleep, etc.) but I would still ALWAYS make the effort to get the lucky girl off either orally or simply with my left hand.
The girls that couldn't climax from that - simply couldn't have an orgasm that day.
Often, they couldn't have orgasms at all.