I agree with both of the above posters.

When you say that your LIFE is crappy, that includes your family. Of course hearing that is going to eventually take a toll on your wife - if you're always saying in earnest that your life is crappy, and then have to go "no no I don't mean you"... which one sounds like the lie? The outburst of unhappiness, or the scrambling to fix it?

You're making an assumption that she knows better. Logically she might, but it's pretty clear that emotionally she doesn't. In all honesty, I would be responding the same as her. I could only handle hearing that someone's life was crappy so many times before I stopped believing them when they said it didn't include me. Especially if I am almost always seeing them unhappy.

Try being more specific with your wife. "Another crappy day at a crappy job" makes it very clear that you are fine with your home life and just in a bad mood from work. You don't even need to go into details about what was crappy at work - and you're still venting the same emotions and frustrations.