From my experience, it is so true that when a door closes, another one (sometimes more interesting) opens up
But what is very true is also that
Sometimes we are afraid to accelerate the process of "opening the new door" because we know what we are leaving, but not what we'll find. But then, how many times do we have regrets for having wasted so much time for nothing?!
I usually try not to regret anything because every experience, even the crappiest one, teaches you something.
So I take everything as a lesson, wether good or not, it doesn't really matter, it is something that made me grow up. But it is really hard sometimes to avoid looking back and wishing things went in a different way.
I am more determined than ever now and I won't let anything stop me.