Look at it from a Freudian perspective - really dumbed down and probably grossly over-simplified, but still: the father, the masculine principle is that which creates and enforces rules. It is the root and the catalyst for the development of the super-ego in children. The super-ego is that part of oneself which constantly reminds one of the rules and regulations, aspirations and ideal to which one should aspire, to which one should ascend, and this is a set of issues which arise with the application of authority. But authority is primarily the creator of rules, not the obeyer. So I would say, from a psychological perspective, that "that which is manly" primarily organizes reality according to its perception and plan. Basically, a man can do what ever he pleases as long as he's constantly aware of his choices and the way they impact on others and on himself. "Being manly" isn't supposed to be something according to a template which you just fill and you stop thinking about it. If you knock out a moose once in a while with your bare hands, doesn't automatically make you manly, in spite of the stereotype. It's awareness of your reality and the ability to act in opposition or in synergy with it, fully aware - that's the tricky part and that's what makes you manly.
On the other hand, no-one said this is a male specific thing, mind you. Women have super-egos to, they are subject to the "masculine principle" during psychological development just as much as boys.
On the other hand, no-one said this is a male specific thing, mind you. Women have super-egos to, they are subject to the "masculine principle" during psychological development just as much as boys.