There's a saying in the racing business. If you're not walking back to the pit now and then carrying the steering wheel, you're not trying hard enough. If you're walking back to the pit too often, you're incompetent.

There's another aspect. If you're launching men in rockets, you cannot tolerate failures, so the development cost is way, way higher. The cost effective method is to launch unmanned ones, tolerating a lot of failures, and when the bugs are worked out then launch men.

If you always fail, you aren’t trying.

If you never fail, you aren’t trying.