Kicking the back of seats and nails on a chalkboard

Why is it that some things just get under your skin and on your nerves, doing a raucous jig, like no other? And yet other things just slide like water off a duck's back?
Now that Andy is back to sitting behind me, I want to just cut his little feet off when he starts kicking my chair. I've tried to tell him that it makes me angry and/or sad, I've tried to hold his feet as a sort of time out, I've told him that it hurts mommy. He just does it harder and more often. I finally just lost it today. I pulled over, unsnapped my belt, and turned around and yelled at him and spanked the top of his feet. I only did this b/c we were on a quiet, residential, side street. So much for my experiment in calmness. It was a complete combo of the annoying kicking and the fact that he just didn't listen. Of course he burst into tears (which I totally almost did too if I hadn't been driving--I felt so remorseful for losing my cool) and then I used my deep dog training voice and told him to stop crying and stop kicking my chair. Lo and behold, both stopped! Instantly! So I have been right all these years, training dogs and raising kids are pretty much the same.
Is it that the deep more masculine voice sends an alpha message to kids just like it does to dogs? Is that why dear husband only has to say something once; whereas, I have to say the same thing in the higher pitched nagging mommy voice several times?
While all this is going on, the baby is screaming bloody murder b/c he's tired and it's bedtime. And rather than be home getting ready for nite-nite, we're finishing some errands for Daddy, who has duty.
I was totally able to overlook the frantic five month old but the two year old just got my goat.
I can handle a kid (not even my own) peeing, pooping, dripping his/her snotty nose on me, crying out of sleepy frustration but I can't handle a toddler being a toddler. Is it because the bodily functions just can't be helped but disobedience can? I need to just come to terms with the fact that my two year old is in toddler adolescence. He's got a newly discovered independent personality and he's testing his boundaries--otherwise known as adolescence. Except with this version I still get a hug, kiss, and snuggle at the end of the day.
So what is it about pet peeves?
Why do some things just get you like none other and some things just can't phase you?
How come I can tolerate my (sometimes) better half leaving coffee cup rings all over my white counters or his leaving the lid off of pots after he's gotten a serving, but I absolutely want to go ape sh*t when he doesn't straighten the damp shower curtain and properly hang up his towel after a shower or doesn't get his clothes into the hamper but rather on the floor next to it?
How about the fact that I can patiently listen to a non-native speaker stumble through the English language but the unabashed butchering of the past tense of verbs and utter disregard of adverbs by a "local" just makes me want to rant (much as I am now). Is this because I grew up with a non-native English speaker (my dad) and a fresh off the plane English (from England) speaker (my mom)?
George Carlin says that anyone going slower than you on the highway is an idiot and anyone going faster is a maniac. I can deal with the turtles and the speedy Gonzales (usually with an under the breath expletive) but the person who doesn't use a turn signal or can't yield when merging makes me want to report them for failure to properly operate their vehicle.
So really. What is it that makes some things just piss you off like a homicidal maniac and other things just leave you (comparatively) feeling as calm as a soul who has just found nirvana?
Let me know before all my hair turns grey and I have noticeable bald spots!