Why do guys (in general) hide their feelings?

I generally don't but i do understand your question, back when i had lack of confidence i was like that, but once i got to build it i became free to express anything i feel and act how i am without worries on what other may think, also our society creates this barriers and rules on how a group or person should act (such as guys and feelings) but the few the have realize those rules don' matter then those are the one you see just having fun and living the life.... just be yourself and and speak your mind....don't worry what other may think.

Here's how crying is dealt with in most families:

Boys: "You quit that crying or I'll give you something to cry about! Don't be a p****y."

Girls: "Oh! Come here sweety. Go ahead and cry. Let it all out. Don't stop until you feel better, okay honey? Okay."

But, that's just fine. Someone has to hold back their tears when real work needs to be done. Men have been selected for this task.

Society seems to believe that showing emotion is a sign of weakness and society doesn't allow men to be weak. It's ridiculous. Society has some kind of hatred toward feelings. Even women who show emotion are seen as whiny, irrational, and bitchy. But I say if you have a feeling, let it out because you are a human being, not a statue.

and women don't, I don't know, i don't hide my feelings. I have to figure when the best time to put them out on display. So i may wait . but in all serious, hide what. Its pretty obvious when i like a girl.

Now women I can't tell if they like me or they want to be friends.

It's all to do with social conditioning.

From a young age boys are told not to cry and to "man up instead" while girls are encouraged to express their feelings.

Men have to be strong. We are not allowed to dwell in the past and cry and whine and moan all the time like women do. In a way that's healthier, because men tend to live in today rather than in the past. Also, we have problem solving abilities that women usually do not have, because we're adaptable to changes.