Yeah, I wasn't sure of how to approach the mental aspect - I didn't mean to say construction or other physical labor required little mental ability, because I've done enough of it to know that's just not the case.
I think coding is different for two reasons - and please do excuse me, because while I've _done_ physical work, I don't do it for a living, so I'm coming at this slanted:
First, with physical work, you're doing, well, physical work. There's a correlation between physical activity and mental acuity, and, as you mention, you can take out some of your stress out on productive labor (if I do that, I have to buy a new mouse). You also have a balance between the physical and mental side - I'm not sure if there's a corresponding mental equivalent to muscle memory.
Second, you can 'outsource' some of the modeling to the actual physical object - the work you're doing has a tangible component, so you don't have to keep the entire thing in your head. That part, to me, is the most draining aspect of coding - I've gotten much better at structuring my code so I can compartmentalize most of that away, but when I'm working with older code or other people's code, I've basically got to have a very accurate representation of the entire program in mind the whole time. That gets really tiring really fast.
I think one of the other big differences, though, is that I can screw up an awful lot more than you can and get away with it - if I completely arse up a section of code, I can go back in and redo it at basically zero cost. If you arse up a floor, well, now we need to buy the raw materials for a new floor. The corollary between experts and amateurs mostly holds between construction and coding - give an idiot enough time and eventually you can have either a house or a program - the difference is he'll cost you an awful lot more trying to build the house. That breeds a level of patience and caution which, frankly, is probably better for one's outlook on life in general.
Anyway, again, sorry if I seemed to demean physical labor - I really didn't intend to. Like I said, I've seen enough experts in action to know the difference isn't in the hands.