For me, I don’t think there has really been one major one; it’s been a collection of smaller ones. Yes, meeting the girl I eventually married was a life-changer, but so were some of the things that happened to me in the Navy, being unemployed for over a year, getting my knee bent backwards by 1500 pounds of sheetrock, and quite a few other things that most people might consider “major” but that happen to me frequently enough that I consider them just another day in my life.