Here's my current interpretation of where pleasure in the current activity comes into it for me: I would play a computer game, which I think should be pleasurable, and used to be, but feel guilty about procrastinating about something else, so I didn't enjoy it as much, or perhaps at all.

If I think about stopping before I've gotten the expected enjoyment, that is unpleasant, so I would avoid stopping or thinking about stopping. I would stop eventually and feel bad about having wasted so much time.

It's not so much that that I picked a game was inherently mind-numbing or unenjoyable, but that I turned it into something mind-numbing because I was avoiding these unpleasant thoughts.