In a paragraph, explain why we often struggle with being truly open about how we are feeling.

This is really a subjective question. In the short story you shared called "The Man Box" there is the idea that male identity or masculinity demands that emotions be kept in a box or away from being shared. Men are afraid of appearing weak or over-sensitive. Females perhaps do not struggle as much with this al males do but vulnerability regardless of gender is a difficult thing to share. People generally want to show that they are in control of things even though this is seldom the case.