I would trust your professor as far as to apply for some top-10 school (and you should in any case, unless you are desperately poor or your profile is absolutely shitty - like 2.5 GPA and 300 PGRE; dreaming is relatively cheap
What do you mean to "trust" what your professor said? You should not do anything differently even if your professor thinks glowingly of you - you still need to apply for safety schools, still have to work hard, still have to write a good SOP, etc. It's dangerous to take your professor's word as voucher and thus becoming smug, and in that sense it's safer for you to assume that your professor is wrong.
In my case, I'm glad that the professor who had been telling me all throughout undergrad that I would have no trouble getting into many top 10 schools changed his tone at the meeting when we seriously discussed the admission process. He warns of the unpredictability of the admission process etc. instead of assuring me of my chance. And that's before I kind of bombed the PGRE according to his standard. That, I think, is the right attitude to have, since unless you got a Nobel prize hanging in your living room, your chance of admission at top school is never 100%.