For starters, I never go anywhere without my phone unless it's the exam room or the shower. The bathroom is debatable, but other than that my phone goes everywhere I go.
So if ever I am out the house and I am without my phone, something is wrong.
I can also never leave the house without money. It just doesn't make sense.
You never really know what could happen out there, who you will need to bribe and what have you.
But really, you can find yourself in a fix if you are ever short for money.