So far, the first thing that come to mind is the day that I got my offer letter for the job that I have now.
That seems a bit shallow, but there's more to it than money, success, etc. I'm not really a type A, look at my job, kind of person. Quite the opposite.
When I got it, it was a win for a lot of people and that's what was/is important to me.
My parents that raised me and gave me the opportunity to go to college.
My brother who was then my mentor.
My wife who held down the fort while I was still in school and in the early years of my career.
Our kids that put up with both parents working, not that that stopped right away but schedules changed a bit to make things easier.