We all learned the rules when we were growing up. Look both ways before you cross the street. Eat your vegetables. Be polite. We all tried - most of the time. Sure, we weaved off the straight and narrow every once and a while, but hey, that's what adventures were all about.
Every new writer learns the rules as well. Show don't tell. Avoid using the passive voice like the plague and cliches are bad. Adverbs are evil. Don't let your sentences run on, but don't let them be too short. Always use 'said' as your dialogue tag.
There are literally hundreds of these rules out there and if I was a new writer, I'd be petrified as well as confused because many of these rules contradict each other. For every time I've seen 'adverbs are evil', I've also seen 'adverbs are our best friends'. I understand run on sentences can be annoying, but if you've a character who is long-winded it can follow that they speak in run on sentences. It happens. Just like short sentences.
When I'm editing I keep a sharp eye out for spelling and grammatical errors (of course) but I'm more concerned about focusing the picture as sharply (oops, an 'ly' word) as possible. If a character is furious, he's going to yell what's on his mind; just as he's going to whisper an endearment. Each character speaks in his/her own rhythm regardless of sentence length (within reason). Some characters like to show off their knowledge and quote works of literature, while for some characters their actions speak louder than their words.
Although each of us has to find our own way on the writing path, I've discovered through pain, error and frustration that that path isn't as narrow as you might think. Feel free to veer off it from time to time. Freedom can be the first step to some wonderful adventures.