I couldn't agree more with what you posted here. Never really thought of marriage as that big of a catalyst though, but you're probably right.
My view is that most people don't actively become the masters of their life, and instead just sail along with the winds, seeing where they'll end up. They're living the life they're living because that's the life they have been living and that's where they ended up; not because they actually consciously made the decision to live their life that way. Everyone is free to live their life the way they want, but I refuse to live my life that way and deep down I'm scared that one day I might succumb to that mentality as well.
I always find it incredibly disheartening when I talk to someone and somehow, everytime I talk to them, they bring the conversation back to a time in the past. Like those were their golden days, the highlight of their lives and everything since then has gone downhill. It's almost as if they've hit the pause button on their life and have stopped living after those golden days. Like the years remaining in their life are going to be filled with nothingness, like they're already dead and are reading their memoires, over and over again. Compare that to the people who energize me by talking about the cool stuff they're doing right now and the amazing projects they've got planned out for the future.