I don't think not experiencing failure can be equated with not being ambitious. Ambition basically means having the determination to succeed. If that determination is there, what is stopping anybody? A couple of hurdles in the path may not necessarily be failures, just lessons along the way. Far more important is one's resilience to face the challenges that come on the journey towards one's ambition.
And the success in what one does should never be quantified....20%, 45%, 70%....see how you achieved it, not how much. Honestly? Without trampling over somebody else? Whether it is a small success or a large one, the manner in which the success is achieved is far more relevant.
When people come at you with their worst, you should come at them with your best (advice given to Selena Gomez by her mother, quoted in Time magazine.)