“The immature mind hops from one thing to another; the mature mind seeks to follow through.”

— Harry Overstreet

Seek to follow through.
Seek to follow through when things are going marvelous.
Seek to follow through when things get monotonous.
And seek to follow through when everything is downright miserable.

Seek to follow through in the good, bad, and ugly moments of whatever it is you’re trying to accomplish. If you do, you'll end up building something invaluable—mental toughness. A one-word description for mental toughness is fortitude, which means, the strength of mind to endure adversity with courage. 

I believe fortitude is one of the most important character traits you can possess. It’s one trait that increases your odds of success because, as we all know, anything worth doing always costs twice as much and takes twice as long to achieve.

Finally, following through is a move toward maturity. It's a concrete way to make the transition from adolescence to adulthood.