I don't if any of you use the Grammarly browser extension but I find it handy. It gives you a weekly report that can be both illuminating and humbling. The most report noted that my most common mistake is to use the comma incorrectly, specifically failing to use it in a compound sentence.
Others might benefit from this resource so I'm sharing it. There are many other sections on how to use punctuation correctly. I warn you that it'd probably take more than one sitting to absorb.
https://www.grammarly.com/blog/comma/
On the plus side, it notes that I use more unique words than 96% of Grammarly users! :-[