Time and using the lessons learned and building them into your future actions as a "growth factor" and as O W Holmes put it ( and it is how I have always understood this poem)

"Build thee more stately mansions, O my soul,
As the swift seasons roll!
Leave thy low-vaulted past!
Let each new temple, nobler than the last,
Shut thee from heaven with a dome more vast,
Till thou at length art free,
Leaving thine outgrown shell by life's unresting sea!!"

"The Chambered Nautilus" is reprinted from The Complete Poetical Works of Oliver Wendell Holmes. Oliver Wendell Holmes. Boston: Houghton, Mifflin, 1895.