You were mature back then, but relative to your age back then. Just as you're mature now, relative to the 18 year old you are numerically. You think back to how you were back then, what happened, and how you responded. How unclear everything was.
That's why patience is a virtue, - it means that you can wait to find out the good or the bad that is yet to come. It means you have the courage to trust that things will work out, or, if they don't that they will fall apart for a reason.
It's nice to be in the position that lets you look back.