Decide Not To Quit.
"Difference in winning and losing is most often not quitting." - - Walt Disney
The above quote says it all. The difference between winning and losing mostly depends on whether you quit or not.
In a marathon, what decides the winner is most often the level of their endurance. Marathon requires patience and tenacity. I have seen people drop out of races half way into it.
Learn to finish whatever you start. Most often, the success story is on the other side of the race. Get to the finish line and see what fate has for you.
Don't be a quitter.
It's never easy but worth it