Musk Reflects on SpaceX's Early High Failure Rate

Musk said that when founding SpaceX, he had friends show him a compilation of rocket failures because he knew the company's failure probability was high.
This is not pessimism, but rather treating high failure rates as a starting point and using rapid trial and error to increase the speed of learning.
In the early days, the Falcon 1 had three consecutive launch failures until the fourth attempt succeeded; this also led the company to form an engineering culture of "test-fail-iterate."
Source: Public Information