Whenever I have tried any text about category theory, it seems to me that it is a catalogue of one definition after another. I am yet to come across (or perhaps missed it entirely) an example use of any of these definitions in practical terms, other than their use in the next definition. It is quite possible that one requires a lot of set up before any it can be used for practical purposes (e.g explaining the basis for all of Haskell's prelude), but I have never made it that far. But I would like to ...

I'd appreciate hearing from those of you who are programmers at heart and have hung in there long enough to gain some insight. What clicked for you?