In some cases you only learn through failure. I learnt more on my first failed Scrum project than I might have if it had succeeded. I learnt that the amount of time it takes to facilitate a team successfully is significant and some of the prerequisites for setting a team up for success. Similarly, retreating off a 2000′ alpine climb in winter taught me a lot about my ability to get out of trouble in bad weather.
Failure in both software and climbing isn’t total if you learn something by it – hence the power of the retrospective. In both climbing and software the object of the game is to complete the goal and setup for the next game. If you don’t complete the project then you can still learn and setup for the next “game”.