What is it that makes a thing "work" rather than "leisure?" Soley that I find it pleasurable or not? I don't think that's intended to be a one to one correspondence so it would help a lot to be more clear about what we are talking about.
The way I see it, work is that which we do mostly to obtain the means for our survival(and for the acquisition of other, more extravagant things). For example, one may work as a programmer. Even if they find pleasure in coding, if they won the lottery, it is unlikely they would keep enduring a 9-5 schedule, demands from their boss, meetings, etc. They do these things because they either need it for their survival, or, at the very least, they do this "sacrifice" in order to be able to buy better stuff.
On the other hand, leisure is what we do solely for the pleasure of doing it, not because we receive something material from it.