How do you know you've been thinking about work too much? When your wife relates a conversation she had with you in the morning, and you don't remember a word, but can definitely see how what you said relates to what you're working on:

Saith my wife: "Jeff, how do you set your alarm?"

My (groggy) reply: "Hit field, the arrow, then default."

Now, this could possibly have something to do with alarm clocks. There