Youve just said it yourself - they seem to be managing things OK. A lot of people are good at putting on a brave face, but when they get home they just cry their eyes out, punch walls, cut themselves etc. I had an ex once who was excellent at making people think she was fine, and then out of the blue she would burst into tears and start shouting at me for the smallest things.

Mr. Pipes, what are your coping strategies for when you feel depressed or pissed off? Some good ones are listening to relaxing music (I choose Badly Drawn Boy), going for a run (releases endorphins, which in turn makes you feel happier and more relaxed), smashing ice cubes (this is a GREAT one, if you ever feel pissed off do this. Its extremely destructive, and it saves your knuckles).
Thats just a few, if you need any more advice just ask, I know what Im talking about here cos Ive been diagnosed bipolar

Hope I helped matey