Used in Steinbeck's Grapes of Wrath, it refers to the self-confidence that men have
1: "fear the time when Man-self will not suffer and die for a concept, for this one quality is the foundation of Man-self" -Steinbeck
1st guy: "Hey, why you so down?"
2nd guy: "I just took a blow to my man-self."
From a meme on deviantArt a man-self is the male version of a female.
Me: This is my man-self, Liam.
Me: He is just like me, but a guy.