I guess it depends on what you want to do in the future, then you can decide whether you want to pursue a subject that is related to that field or pursue another field which interests you, ok, so that was kinda a mouthful, so I'll give an example
I've always wanted to do Medicine, but I'm also interested in other things, namely Maths, IT and Physics, so even though I could have done Biology, PE or HHD which would be a little more related to Medicine, I decided to do Software Development, Methods, Spesh and Physics because it was a chance to pursue some interests before going into Medicine, after which there would be little opportunity to pursue those interests. I'll end up doing Biology and stuff anyway, so my logic is "why waste a year 12 subject on it, if it's gonna be repeated in uni!"

- And I guess in the end I was happy with my decision.