MacBook Pro Retina- protect or leave as it is?

Hi.

I am a student and naturally as every student's computer my mac is going to go through some tough times. I know for certain that it going to be in my bag a lot, and also would meet plenty of unfamiliar surfaces. So i want to preserve at its best, without giving up anything.

I've heard about protective cases, and actually gone through two with my previous mac, but i can't say i want to repeat the experience, since the device is unable to breath once clad in all this plastic armour that in the end does more harm than good. Well yes, at first it looks all that shiny and beautiful, but when the time comes you realise that it isn't. So generally i do not advocate hard-shells and everything of the sort.

Also i have a backpack (bought in apple store in London) which doesn't really reassure me, and i can't feel that my MBP is really safe in there.

I do not want, however, to have a couple of tonnes on my back.

So what could be your suggestions? Is there anything to buy for some extra protection or i should leave it the way it is and just peace with scratches and everything?