I think what most people (CrossFitters and "civilians" alike) don't realize is that the WODs that we do are designed to CRUSH elite athletes - no I mean really crush them. So when you do a WOD as RX'd (or even close to it) and you can't walk normally or raise your arms above your head then it's your own fault! Not being able to perform daily functions (walk, eat, wipe, etc.) because you destroyed yourself the day before is just plain stupid... and could be potentially dangerous.
So, how do you approach the WODs then? Do you just not do them or do you learn how to scale them? Well, according to Greg Glassman, most if not all people doing the WODs should be scaling them in some way or another... and he's said this more than once.
So how do you know that you're scaling the WOD the right way? A good rule of thumb would be to scale the WOD to no more than 80% of your max effort, and even then, that may be too much. Remember that every WOD is not an opportunity for a PR, but it is an opportunity to improve your overall strength and conditioning. If you are trying to PR every WOD you are going to find yourself perpetually fatigued and potentially sick... something you don't want to do if you want to keep moving forward.
Another thing you want to think about is how the body adapts to extreme stress - like a WOD. If you are in a constant state of stress then your body will not adapt in the way you intend it to... in other words, you will have limited muscle development, aerobic adaptation, etc. Several studies have shown that working at 80% of your max effort will allow you to continue to get stronger without over-stressing your body.
BTW - the picture has nothing to do with this subject. I just wanted to show what the evil box did to poor Chris!!! After we taped him up he went on to finish the next four rounds of the WOD. Then sometime later that night he went to the ER to get 06 stitches in his right knee and the left knee cleaned up and bandaged as well!!!