Even with an A 40 is pushing it, although it does depend on the subject.
Take further last year, a friend of mine got A+, A+ and A+ and ended up with a 41, not much above 40.
For Chem this year, I got an A on mid year and knew it was going to be hard to crack 40 after that, I worked my ass off hard for the rest of the year, really pushing it and ENDED UP WITH A 39! I was so close, but nevertheless I'm happy with it. Results ended up being A, A+, A+.
For spesh this year I got A+, B+, A+ and ended up with a 41. I did a couple of stupid things on the spesh exam 1 and so dropped at least 5 marks, hence the B+ (probably a high B+ though). Since it was the exam 1 (and it was a maths subject), it is weighted less, i.e. SACS: 34% Exam 1: 22% Exam 2: 44%. So I probably got lucky that I screwed up the right exam.
So it really comes down to the subject and what part of the assesment it is. Also as you work hard throughout the year, you can't do anymore and should do well, having no regrets.