What is the most valuable or helpful lesson you can learn from life?

I’m not thinking of something philosophical or religious or high-minded—at least, not necessarily. I’m wonder what valuable lessons there are that can only be learned through the experience of life. This is experiential, not mental or theoretical. Things like having lost in love, or having and bringing up children, or having loved, or having overcome some obstacle. What of these, or many other life lessons would you call the most, or close to the most valuable?