The inexorable hand of experience
Alas, Experience! No other mentor has so wasted and frozen a face as yours, none wears a robe so black, none bears a rod so heavy, none with hand so inexorable draws the novice so sternly to his task, and forces him with authority so resistless to its acquirement. It is by your instructions alone that man or woman can ever find a safe track through life's wilds; without it, how they stumble, how they stray! On what forbidden grounds do they intrude, down what dread declivities are they hurled!
...
many a wilderness, and often the flood of death, or some stream of sorrow as cold and almost as black as death, is to be crossed ere true bliss can be tasted. Every joy that life gives must be earned ere it is secured; and how hardly earned, those only know who have wrestled for great prizes. The heart's blood must gem with red beads the brow of the combatant, before the wreath of victory rustles over it.
-Shirley
by Charlotte Bronte
(one of my all time favourite books)