Imagine working for a small firm and having the boss/owner tell you all of his fears for the business. If you are relying on that job to support your family this could very quickly become unsettling. The same is true if your surgeon, dentist, or airline pilot doesn’t communicate confidence and a command of the situation.Hiding your concerns is probably not a good idea, since she'll always pick up on your feelings and will likely imagine them to be worse than they are. But don't look to her for emotional support and a shoulder to cry on. She's looking at you to demonstrate that you are worthy of her reliance upon you. So be honest about the situation, but don't look to share your feelings or unburden yourself.
Your wife (and even your girlfriend) wants you to be her rock, especially if her own emotions are storming over her. This is a profound gift a husband can give his wife, and should not be seen as something negative. A wife also relies on her husband for protection and financial support of the family. For these reasons there is a limit as to what kinds of things and more importantly how, how much, and how often you talk about these things with your wife. This isn’t because there is something wrong with women, it is due to the difference between men and women, and more importantly the nature of the roles of husband and wife.
However, this doesn’t mean you should shut her out when something is troubling you, it just means there is a balance. Especially after you are married for a number of years, your wife will know when something is troubling you. If you pretend that nothing is bothering you, or refuse to discuss it at all, this could be even more unsettling to her.
Your wife should be your cheerleader, not your therapist.