Mehdi Osman applied three times to Y-Combinator. On the third time he made it. Osman credits the maturity of his startup Asayer's service that helps developers hunt down and kill bugs in their code. But also just straight-up determination. "At some point you make your own destiny," he says. Why Osman still relies on email, spends as much time with customers as possible, and doesn't believe the hype -- pivoting is the worst.