Very well said. I might go so far as to point out that, roughly speaking, variety -> mental stimulation -> pleasure -> one source of utility. I would therefore anticipate that doing the same thing all the time is suboptimal for almost everybody, except in cases where the utility lost by the specific change obviously exceeds the potential gain from the mental stimulation. (I don't need to get shot in the stomach in order to make sure it's not more fun than what I normally do.)

I used to know someone who, when he was younger, had precisely this problem. He had learned that he liked cheeseburgers a lot, and therefore could see no reason to eat anything else when he had a choice. He went so far as to request them when he was at a restaurant where they weren't on the menu. He grew out of this, eventually, but I'm not sure he ever grew out of the mindset that led to it.

Also, this seems like a good place to recommend a specific technique along these lines. A while ago I made a list of activites and posted it on my wall with the heading "More Useful Things to Do Than Fucking Around on the Internet." (It's my bedroom and I can be profane on the wall if I want to.) Entries include chores (laundry), things I mean to do more often but don't get around to (call a friend), things I forget about when I'm looking for something to do (go to the library), skills I want to learn (knitting), projects I have in progress (clothes making/mending), etc. The point was to prevent myself from ever claiming that I don't have anything good to do. There's always something good to do. I just sometimes need to be reminded what it is.