''to draw Dragonball in a long time produced a very complicated mix of emotions, combining nostalgia with the feeling that he dind't want to draw Dragon Ball anymore.''
Maybe he doesn't like drawing Dragon Ball anymore.
I think he had a bad experience with Dragon Ball. He must have been under extreme high pressure making those new episodes every week, I couldn't even keep up my manga, I can't imagine what it would have been like if I had to make a new chapter every week. I would end up dreading ever going back there once I finished. Instead of ending it where he wanted to and ending on good terms, he probably bid good riddance to it.
He ended up being peer pressured by some anime producer or assistant or someone to keep it going on. Don't get me wrong the Buu saga is as good for me as them all in it's own way. I am not at all dissapointed that Toriyama carried it on rather than ending it at the Freeza or Cell stories.
But doing that kind of work every week would make you sick of it eventually, and it's not very nice not enjoying your own work. I'm not saying he did, but if he doesn't like the emotions he experiences while drawing Dragonball, maybe he remembers staying up 'till daylight and losing sleep drawing the same characters over and over again, eventually develop some type of hatred with Goku's face similar to Sideshow Bob's for Bart, and with Cell's body spots, well, he admits he made a mistake there. Dug he's own grave really.

He was probably thinking of the next story lines in he's sleep, it would drive you nuts, probably having dreams about flying on Kintoun over the land.
He said he was losing time with he's family, and it's one of the resons he stopped drawing Dragon Ball, to spend more time with the wife and kids, he is a family guy. I think when the anime finally ended he was so relieved, he could finally put he's feet up, do more things he couldn't really do before because of time being used up. And this is probably why he doesn't really feel like drawing it anymore.
This is another reason why we most definately will not see the story continue by him, and I don't blame him, who wants more?
I'd much rather they re-released those whole manga in colour.
Also, sorry to make 2 threads, you know I rarely ever do. I don't think this subject has been disscussed before has it?