Men tend to withhold things for decent reasons. Not wanting to worry her, not wanting to look like you are not handling it, wanting to sort it out before it becomes a conversation. The problem is that almost none of these get smaller while you sit on them, and the damage usually comes from the concealment rather than from the thing itself. Here are twelve worth saying out loud.
Debt and What You Actually Owe

The most commonly hidden thing in relationships and the one that does the most damage on discovery. If your finances are joined in any way, she is already exposed to it through joint accounts, shared borrowing and mortgage applications. Finding out from a letter is far worse than hearing it from you.
Losing Your Job or Taking a Pay Cut

The instinct is to fix it quietly and tell her once you have a new role lined up. Meanwhile she is making household decisions on numbers that no longer exist. Every week you wait makes the eventual conversation harder and the financial hole slightly deeper.
Symptoms You Have Been Ignoring

Men are consistently slower to see a doctor, and the delay is what turns manageable problems into serious ones. Telling her means somebody else knows and will keep asking, which is precisely the point. If it is embarrassing, remember your GP has seen it several times this week already.
A Diagnosis You Have Already Had

Protecting someone from news about your own health takes the decision away from them. She will find out eventually, and at that point she is dealing with both the diagnosis and the fact that you carried it alone. Very few partners are grateful to have been shielded.
How You Are Genuinely Doing

Fine is the default answer and frequently not an accurate one. Persistently low mood, sleeping badly, drinking more or losing interest in things that used to matter are worth saying plainly to someone who wants to know. If it feels impossible to raise at home, a doctor is a perfectly good place to start.
Big Purchases and Money You Have Spent

Small concealments compound. Hiding what something cost, or that you bought it at all, creates a pattern where money becomes the subject nobody discusses honestly. If a purchase would require an explanation afterwards, it is simpler to have the conversation before rather than after.
Contact With an Ex

The contact is usually not the issue. Hiding it is, because concealment implies there was something to conceal, and that inference is very difficult to undo once it forms. Mentioning it casually the same day costs you nothing. Explaining it three months later costs a great deal.
Doubts About the Relationship

Unspoken resentment does not stay at its original size. Problems raised early tend to be solvable, and the same problems raised after two years of silence arrive as a verdict rather than as a conversation. She cannot address something she has not been told exists.
What You Actually Want

Including in bed, and including the ordinary things like wanting more time alone or less of a particular routine. Expecting a partner to work it out unprompted is a common and unfair arrangement, and the resulting frustration usually gets blamed on her rather than on the silence.
Your Family Medical History

If there is a hereditary condition in your family, that information affects your children and what screening they should be offered. It also affects decisions you might make together. Many men simply do not know their own family history, which is itself worth fixing with a phone call.
Where Everything Is If Something Happens to You

Passwords, insurance policies, the will, account details and who to contact. Families routinely spend months reconstructing this after a death or a serious illness. A single document she knows the location of removes an enormous burden at the worst possible moment.
The Line Between Privacy and Concealment

None of this means she is entitled to every thought in your head. Privacy is keeping something that affects only you. Concealment is withholding something she needs in order to make decisions about her own life. If she would act differently knowing it, she should know it.