Professors are people too. I know, it’s hard to remember that sometimes, what with them holding your life in the balance, but it’s is true. That means they’ve got their expectations, their pet peeves, their wants and their fears.
Also, remember that you might think you’re busy, but that’s generally nothing compared to what a professor has to deal with. Not only do they have to teach classes and read all of the classes’, but they’ve got to conduct research, write up papers for peer-reviewed journals (whose demands put your assignments to shame) and survive in the publish-or-perish atmosphere of academia.