You're not alone: my partner and I are arriving into Toronto from Dublin on September 5th and that's when he'll land. He's really freaked out about the whole thing, a real worrier, imagining all sorts of crazy, worse case scenarios! Some of them quite hilarious! Don't know why. All I can do is reassure him and you that you're in a better position than most people arriving at the border: as far as the immigration officer is concerned, someone has already done all the work thoroughly checking you out. If that person was happy enough to issue the visa, then this officer is not going to go out of their way to make things difficult, for you and for themselves! Can you imagine the paperwork involved if she/he refused you? The landing process seems to really be just a formality. So unless you're obviously diseased or have a set of handcuffs hanging from your wrist, I'd say you're fine.
Good luck!
Tara