Experience !

Experience is the comb that Life gives you when you get bald !
-- A Chinese (or Thai) proverb.

Experience is what you got by not having it when you need it.
-- Unknown

And here comes the best of the lot...
Experience is what causes a person to make new mistakes instead of old ones.
-- Unknown.

Run !

“Every morning in Africa, a Gazelle wakes up. It knows it must run faster than the fastest lion or it will be killed. Every morning a Lion wakes up. It knows it must outrun the slowest Gazelle or it will starve to death. It doesn't matter whether you are a Lion or a Gazelle... when the sun comes up, you'd better be running.”

- Unknown (to me).

Another thought...

Those who want to fly... must know the importance of running on the ground

-- Viral Shah