How do I find out which job I don't suck at?

[Lyshell]

Plus liking a job can be used as motivation to get better at the job.

Play what you enjoy playing. If you're "bad", then practice.

I think this sums it up pretty well. I can understand too that some people can only enjoy a job if they're doing the best they can on it. So you could love a job and practice the hell out of it and never be "good". It's up to you though and like the previous posters said passion is key. Good luck OP!

[Cnidarian]

I agree with the others, play the job you have the most fun as. If that isn't an option for you for whatever reason, then you could always hit up the SSS for your appropriate ilvl and see what you perform the best as.