I don't see what "how intelligent you are" has to do with choosing a career .. if you don't like what you're doing, what's the point?
Obviously Dan is trying to choose something he's interested in & isn't asking whether people think he should be an astro-physicist or whatever ..
@Dan .. IMO take a year off .. work, travel, figure sh*t out .. try a few different jobs if you want .. there is nothing to say that you "have" to go to Uni / Tafe the first year out of school & the best time to figure out if you want to be a mechanic is 'before' you pay thousands of dollars for a tafe / uni course.. hell .. If I could do it again I would have taken time off to work .. if nothing else, it means that you qualify under Centrelink law for Independence status if you earn over a certain amount since leaving school .. meaning that when you finally do decide to study .. or you're between jobs that you're trying out, you can go straight onto Centrelink without having to jump through hoops proving your parents income etc
The worst thing for me while studying full time in my first year out of school, was that you can't just go on centrelink & get the full amount, you only get a fraction of the full cost / nothing at all if your parents earn too much & you can't work, because you're always busy..
Anyways .. from personal experience, and I can only speak for myself .. but I don't think I was disciplined enough to want to put in the effort in the first year out of school ..
I'd just spent the last 12+ years in school & was kind've over it (probably like you are feeling now) so I was kinda slack about my study.. if I went to Uni now, after working for a few years I'd probably be more likely to put in the effort & not slack off.. but oh well..
anyways mate .. don't take people's comments too seriously

99% of the time they're just stirring the pot..