Babies learning how to walk will fall…get up…try again…they do this over and over until they succeed. They are failing fast…and trying again…parents encouraging them to get up and they do…then eventually babies — learning from their mistakes — start walking. Success!
You do the same with your ART; give your Agile teams and team of Agile Teams the environment that allows them to fail..to fail fast, encourage them to recover fast, and try again for success. Such environment is a safe environment. Pun intended…because SAFe actually has a principle for this: Principle #4 — “Build incrementally with fast, integrated learning cycles“. Learning Cycle, in a nutshell, is the PDCA cycle: Plan, Do, Check, Adjust. 
When building a system incrementally, it is best to have PDCA cycle in every integration point…this allows you to adjust for correction sooner rather than later.
Thomas Edison was famous for never giving up in his search for the construction of the electric light bulb — Edison applied this PDCA cycle. Edison said, “I have not failed. I’ve just found 10,000 ways that won’t work.”
So, yes, aim for progress, not perfection. Being comfortable with imperfection, uncertainty, misadventure, and failure allows one to be progressive, bold, innovative and adventurous. Allows one to assume variability and preserve options — SAFe Principle #3 — to achieve optimum result.
An environment that does not allow / tolerate failure will find itself failing overtime. In this day and age, innovation is key to success. In our earlier example, failure taught Thomas A. Edison to repeatedly innovate.
