Great post.
I’ll just toss in that at this point, I have known a lot of people who went to highly-selective educational institutions, and also a lot of people who have had a lot of professional success. There is some overlap, as one would expect, but it is VERY clear that overlap is only partial. Many people I know who went to the very selective educational institutions have done reasonably well, but no more so than you would expect for anyone with their degree(s) from a solid institution. Many people I know who really achieved at an extraordinary level professionally have ordinary, or indeed pretty obscure, educational resumes.
So yes, it truly is always about you, and what you make of your opportunities. And by the way, there is nothing wrong with going to a very selective school and then having a fairly ordinary, but generally successful, professional career. Many of those people have great families, and fulfilling lives in general, and their professional careers gave them what they wanted without subtracting too much from other parts of their lives.
All this just underscores you should always be thinking in terms of actually valuing the years you have. Your life has already started, and these years count as much as any.