Grammar mis-habits we don't want to change?

I know there are grammar habits that are hard to break when we know they should be otherwise, but I just saw someone confess that there are grammar rules they know and refuse to conform to because they just feel too wrong to obey. That's a little freeing, because I suspect a lot of us have at least one of those somewhere.

I know, for example, that there are a few words I britspell no matter what. "Traveller" will always have two "l"s when I write it, and there can be "mold" on cheese but I pour Jell-O into a "mould." My brain rebels at the alternatives.

Anyone want to confess theirs?

Original fiction: Muscle Memory, Chapter Fourteen

Chapter Fourteen of Muscle Memory (free chapters available here) is up at SL Publishing.

( Teaser below the cut )

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Go here to read Muscle Memory, Chapter Fourteen!