One certainly can decide for oneself when to use a comma and when not. The problem with Lawler's advice is that commas are a visual tool, not a verbal one. No punctuation is ever verbalized, and when speaking, people often pause where they would never include a comma in writing, and speed through sentences that invite punctuation of various sorts at several points. Furthermore, how can a listener tell from an intentional verbal pause whether this point represents a comma, a dash, a semi-colon, or a parenthesis?
I don't dismiss Lawler's advice, because comma usage often does follow speech patterns. But punctuation is generally intended to aid readability, and how one speaks should be at best one consideration among several in how to use commas. But there are no rules, only conventions. And inasmuch as conventions are, by definition, widely known and adhered to, you can generally assume that writing that abides by convention will be more accessible to more readers than writing that does not.
Of course, as demonstrated by many great writers, the best of the Lost Generation and the Beats, for example, flouting convention is itself often a worthwhile pursuit, leading to the dismissal of outdated approaches in favor of new, more relevant ones, which in turn become conventions themselves in need of overturning. Gertrude Stein once wrote,
So now to come to the real question of punctuation, periods, commas,
colons, semi-colons and capitals and small letters. I have had a long
and complicated life with all these.
Language is an ever-evolving phenomenon. The "rules" of grammar, IMO, are merely a guideline, a template if you will, that may be, and should be, amended to suit a writer's individual purposes, without alienating his or her intended audience. As Stein implies, punctuation is complicated. And that's what makes it (or the lack of it, in her case) interesting.