When you're cold, wet, and tired it helps to pretend you love it. It's infectious, too.
It is actually a good feeling when you realize you're not as fragile as you thought you were. "I would have thought that I'd be miserable in this situation, but I'm actually OK" is a good thought to have.
https://www.scientificamerican.com/article/smile-it-could-ma...
https://www.psychologicalscience.org/pdf/StrackRRR_manuscrip...
The problem with this phrase is that the U.S. military takes it extremes, telling soldiers to suppress inborn capacities for empathy, particularly in regard to civilians and "military-age males" routinely maimed and butchered in the course of its day-to-day operations. Inevitably resulting not only in mental health issues for the soldiers when they return home, but ultimately, failure of the overall mission itself.
The phrase used in the US military for this is "Embrace the suck". Which means "The situation is bad, but deal with it."