[T.B. Yoits]

Those who don’t have their nose to the grindstone are often disheartened by the truth they see, which those with their nose to the grindstone don’t.

[RoosterRedux]

And those whose noses aren't against the grindstone don't understand the concept of being personally invested in something (i.e., time, work, and commitment).

The more one has invested, the sweeter the payoff when the day is done and the job is finished.