(not) the be-all, end-all of (something)

(Not) the most important event or thing relative to some particular thing, situation, or event. My little sister thinks that a date with the captain of the football team is just the be-all, end-all of her life right now. I once thought that not getting into Harvard was the be-all, end-all of my academic career. Thankfully, I was wrong. Being sent down to the minors is not the be-all, end-all of your season—it just means that all the veterans on the team are healthy right now.