stay the distance
1. To persevere with as much determination, energy, or fortitude as one can muster through to the end of a race, competition, or contest. Despite an early setback in the first half, the American team stayed the distance and managed to earn a draw at the end of the match.
2. To continue attempting or pursuing something difficult to its end or conclusion. If you can't stay the distance when things get a bit messy, then you just aren't cut out for this line of work.