Why is opening up so hard?

Because you don't know how someone else will react.

People generally don't like confrontation, so you might seek to avoid it. Then there's the prospect of being shamed for how you really feel, villainizing you for simply feeling a certain way.

It's not because you're a man who was told to be a manly man and shut up, but because it's your self-preservation instinct. Why invite trouble when you can avoid it?

I think we all reserve some private thoughts if we are honest. Why? A number of reasons one is they are our thoughts to share or to keep. It's not a bad thing. Unless your concealing something sinister,criminal illegal etc.

Very probably. I can't share with my husband because he does not share with me. If a dialog began, I could easily fall into step with my own thoughts, but he doesn't appear to be interested.

Maybe your conditioning as a male that it's wrong to show and share deeper thoughts and feelings

I think it's a part of every relationship. Whether a relationship with a fellow passenger on an airplane, a coworker, parent, relative, neighbor, spouse. We open up when we get a positive feeling from the relationship, like we feel like the other party wants to hear what we have to say. If we get a negative feeling we shut down. Rejection is just another form of disinterest. Mistrust comes from negative disguised as positive, like we are being tricked into believing there's a positive interaction.

do you hold back because you think it's weak? That's a common reason men don't express their feelings

Sounds like you have something to confess.

I don't know..I would think all desires would be known within the first few weeks of knowing the person.

Because alot of married people love to stop communicating with each other for some reason once they say "i do"

You won’t know until you ask. Good luck.

It's okay, tell her your kinks.