Boo Boo Foo,
You lost your temper for a moment and acted inappropriately by your own standards. You should not beat youself up (heh) over it. The fact that you feel bad about it speaks well of you.
FWIW, placing some form of protection over your leather upholstery is an excellent idea while your daughter is young, because accidents do happen. However, I don’t think you have to worry about your child intentionally making a mess in the back seat again. That lesson has been learned, and at an early enough age that it may stick. Could it have been learned without the smack? Probably. Just an angry tone of voice will often do the trick. But not always, and not with every child.
Children may be born innocent, but they are not born with a sense of propriety, or good judgement or manners. They learn these things through interactions with their environment and by the teachings of their parents. They also learn very quickly to avoid things that cause pain. They won’t touch a hot stove twice, or run through a sticker patch barefooted, or stick a paperclip in an electrical outlet more than once. Likewise, when they need to learn to avoid behavior that may not instantly result in pain, but is nonetheless vitally important, a spanking puts a concrete face on an abstract concept. In other words, when they do something dangerous and get away with it, they don’t learn that it’s dangerous. But when that action results in a couple of solid swats on the butt, they think twice about running with the scissors or teasing the neighbor’s rottweilers.
Corporal punishment, when applied appropriately, is a very effective means of instilling good behavior in children. Unfortunately, when applied viciously or capriciously it can also be an effective means of creating a violent sociopath. For this reason, the consensus seems to have shifted from “Spare the rod, spoil the child” to “Spanking is child abuse”.
Most of the people I know were spanked as a child, myself emphatically included. Only a relatively small number of them grew up to be violent wife/husband-beating, dog-kicking, cat-drowning, child-abusing adults. Obviously there is another dynamic at play here. For my part, I think that spankings should be applied sparingly and judiciously and always explained afterwards. Also, once done, the transgression which led up to the spanking should be considered forgiven in full. It should never be held over their heads again unless the deed is repeated.
It’s not easy holding the middle ground, so I am sure that the spanking/no spanking pendulum will likely continue to swing back and forth for many generations to come.