Los Angeles Times: L.A. Affairs: I swore off cats. Then I met my dream guy who had one
L.A. Affairs: I swore off cats. Then I met my dream guy who had one
MSN: LA Affairs: I swore off cats. Then I met my dream guy who had one
LA Affairs: I swore off cats. Then I met my dream guy who had one
It is used to describe experiences one has had in the past (and that hence influence the experience with which you speak today), changes over time, uncompleted actions, and things that have happened more than once.
The first one basically just emphasizes the order of events - that you had already eaten too many chocolates before dinner, and as a result were not able to eat any more. The second one doesn't technically make it clear that you had eaten the chocolates before dinner, but then again it's really the only possible meaning in that context so the two sentences don't really have much difference in ...