Trust me. He's not a loser. I'm not cut out for a number of things. And there have been times that managers have "let me go" in the first 2 weeks telling me that I'm not "good material" for that industry, only to find myself as "acting" general manager in the same industry a year later. My advice is simply this:
1) just because you performed poorly (if you even did) at a job, doesn't mean you will do poorly under different circumstances, management, or job area in same industry.
2) sometimes, a bad boot to the butt out of a job allows for opportunities to open to you. Or you may rethink your position or where (or what) you want to do for a living.
3) everything defines us. Maybe this is a defining moment (not the actual firing). You should look at yourself and determine why it didn't work. What would you rather be doing. Nothing? Me too. Though we both know that doesn't really work.
4) Like your wife has already said, you do better in an office environment and not a travelling rogue. That's what I mean by defining. When others see something like that, you should definately look at that.
5) Your work doesn't define you (that's not what I meant as a "defining moment"). Though I fully understand your desire to enjoy the work that you do. Something fullfilling that pays well, right? One step at a time, sometimes. Maybe looking for something you're interested in, but in an office environment.
6) It sucks. Recognize and embrace that, then move towards less sucky situation. Goal in life..."something that sucks less than where I'm currently at."
7) You have a fantastic wife. Relish that. My wife is equally fantastic and sometimes confused as to how to advise me in situations like this.
Positive thoughts your direction.