While there are some actual rules around the use of commas in English, I feel that many are simple guidelines that illustrate how to use commas to write English with the significant pauses you hear when it is spoken. So, their use is as much personal style as accent or word choice.
Consider my last paragraph, for example. I could have inserted or omitted commas in a variety of spaces including right here but I haven't because it's not required. Or, alternately, I could include a great many weighty, significant commas, since, perhaps, I'd want to break up the sentence into separate thoughts, as if I was talking slowly, or haltingly, or without a clear idea where I was going.
It is important to understand the basic rules for using commas, such as those here. You should certainly study and practice these until they become habit -- but understand that once you get past the basics, it's more about the writer's voice than any inviolable grammar.
Consider this passage from the opening scene in Cormac McCarthy's novel "No Country For Old Men":
When he stood up out of the chair he swung the keys off his belt and opened the locked desk drawer to get the keys to the jail. He was slightly bent over when Chigurh squatted and scooted his manacled hands beneath him to the back of his knees. In the same motion he sat and rocked backward and passed the chain under his feet and then stood instantly and effortlessly. If it looked like a thing he'd practiced many times - it was. He dropped his cuffed hands over the deputy's head and leaped into the air and slammed both knees against the back of the deputy's neck and hauled back on the chain.
Nearly all of McCarthy's writing is like this. Which isn't to say he never uses commas, but he writes as if he's telling you a story in one long string without pausing for breath. That's his signature style, his voice.