Even though I enjoy the S, I think the most valuable letter for me is the P.
Like Pika said, the P allows you to adapt. It helps me be more open-minded and exploratory. There are many wonderful experiences I've had, all thanks to the P. If I had been a J, I think I would have missed out on so much.
The P opens the door to risk-taking. This can lead to great failure, and, more importantly, great success.