I will only lock my car using the button on my key, not the switch on the door. I only lock my door behind me with my key rather than setting it to lock behind me. Any time I'm about to let a door close behind that will lock behind me I have to be touching my keys or if it's keycard actually take my wallet out and look at my card.
It's taken many mistakes over the years to get these habits engrained, and even then I still make mistakes. A few weeks ago I lost a check for $1600 that didn't have a name written in for payee. I put it in my pocket and was immediately going to write in my name once I got home. Got home and couldn't find it. Fortunately the person who wrote it was able to contact their bank and cancel it, but yeah, that could have been a very expensive mistake.