I feel like you're looking at this the wrong way.

Are you recently out of school, by any chance?

I still feel like you have this deficit-oriented "English class" approach to writing. You're acting as if someone's out there ready to go through everything with a fine tooth comb and find flaws in it, so as to give you a lower score on something.

Put that behind you. That's not your world anymore. You're rendering a service to people now.

No one is hovering over your drafts, looking for a wrong semicolon so they can be like, "Whoops, that semicolon should be a colon. Sorry! We're not paying you for this. F - - . You'll never work in this industry again."

Things like fixing a semicolon are the underlying reasons that publications have editors in the first place. That's literally their job.

Look. You can't go through life with this "deficit mentality," where you're convinced that nothing you do is ever good enough.

It's not healthy. And not only is it unhealthy, but it can lead you into situations where you're being taken advantage of.

Most of the time, your natural, intuitive grasp on what is or isn't grammatical in your native language is all you really need.

If you're not sure, consult Strunk & White. Also, question whether you need a semicolon at all if you're not sure how to use it.

Stop being insecure about this. It's not worth being insecure about. Chances are, your grammar is absolutely fine. Also, editors exist. You will have trouble selling yourself and your value if you keep putting yourself down for bullshit reasons.