Driving a heavy goods vehicle you will be subject to more noise, changes in temp, delays and frustration plus the aggresion of other road user's, in an aircraft you can let your guard down at times (go down the back for a piss) and there are at least two of you.
I guess it's different for different people but I disagree with you on this. I have driven trucks for a living and currently fly 73's on short haul.
I think that the reduced oxygen of being at a cabin altitude of 8000ft for seven hours a day has a significant effect. Also, with 30 min turn arounds and five or six sectors there is very little time to relax. A ten minute break, out of the aircraft, sitting in a crew room would set me up well for the second half of a day but unfortunately that luxury is long gone. I used to enjoy it when we could do this, it was a social time as well and seemed to ease the mental stresses.