I have one of those wallets that has grown into a small filing cabinet that you keep in your back pocket. If you back aches, you may have one of these. My chiropractic brother encouraged me to not sit on this wallet all day long as has been my habit. So I went through a long period of leaving the house and driving around town without my driver's license since my driver's license was in my wallet sitting on my desk.
One day this year I found myself speeding around town trying to make appointments in a vehicle that had no insurance, expired tags, without my driver's license, low on gas and with no money. Murph let me off that time.
So I adjusted my habit and now if I take my wallet out of my pocket I put my keys with it. Can't leave the house without the keys and if the keys are with the wallet I won't forget the wallet. One caveat... where the blazes are my keys?!