For me, I cannot leave the house without first letting my dog out, petting at least 1 of my two cats, and double checking my pockets before I shut the door to make sure I have my keys. I have an inherent fear that one day I'm going to lock myself out of my own house and be stuck outside for hours until my husband can come home with his keys, since we don't have any extra 'spares' just 1 key for each of us on our separate key rings.