Congrats. Welcome to the real world...
First, you will have to train yourself to forget Windows-think. There isn't a lot you need to do to keep your Mac running well. You don't need to defrag the drive, ever. You don't need to install anticrapware programs, as there are zero true viruses in the wild which affect modern OSX installs. True, there do exist some Trojans, and some malware/spyware, but the only way to get those is to install them, and give the admin password. Bottom line, don't install warez or cracks.
Beyong that, don't drop your Mac, don't take it swimming, and don't attempt to eat it. Other than that, you will love it for years to come. You will probably stop using your new Mac when you upgrade to the newest shiny Mac that comes along... And then, you will enjoy nice resale value, far better than most pc resales.