I remember sitting up late one night in my twenties overwhelmed by the sheer number of doors I would never open. Not metaphorical doors--actual, physical doors to physical buildings and rooms. It had hit me earlier that day that the number of doors I would even encounter in my life is infinitesimal compared to the total number of doors, and the ones I would open of that tiny subset were orders of magnitude smaller still.
I suppose I could have responded to this by making some strange life rule where I always try the handle on every door, but I think I grew a lot more by deciding it doesn't matter, that opening all the doors, or even maximizing my chances to open doors, would be a waste of my life. So I guess they doubled as metaphorical doors after all.
I don't know how measurable it would be, but I would rather measure my personal growth by the peace I've managed to find with the realities I can't change and the choices I've made. For instance, I'm not infinite. I'm going to die. There will be things I dislike about the world that won't change during my lifetime. Stuff like that. That seems like a better measure to me of how much I'm growing.