Freemasonry, which I'd describe as a sort of meta-framework for living a good, ethical and worthwhile life.

Freemasonry among many other aspects can serve as constant reminder to behave ethically and make the most of your life.

It also allows to get to know people from all walks of life and backgrounds that otherwise you probably wouldn't have met. Apart from being a great way to discover novel ideas and broaden your horizon this also helps with becoming more tolerant towards others who don't share your background or points of view.

Although the question implies just one thing I'd also mention having worked as a paramedic for some time.