English is a complicated language, filled with exceptions to spelling, endings of words, and general usage. Even pluralizing is a nightmare; you almost have to check the dictionary to see how to spell the same word as you apply it to different sentences.
You may have to double or drop the last letter, or change the spelling entirely.

Reading a lot teaches you to recognise a word that doesn't "look right." But correct grammar comes more from memorizing exceptions than following the rules!

Has anyone else ever read Ferlinghetti? He wrote without any Capitals or punctuation marks. Now that is getting written word to imitate spoken language, full of ambiguity and the potential for misunderstanding!

I love to edit, too. But worry that pointing it out will meet with defensiveness. No one is perfect, and "bad" grammar doesn't really bother me.