I used to have some interesting discussions about theology with a grocery store worker.
"Where's the line between what's predetermined in our lives and the free will we have?" I once asked.
"Here's where the line is," he replied. "Do you know what you'll be doing at 2:00 next Tuesday afternoon? God does, but how you react to that situation will be up to you."
Obviously, your mileage may vary, but I thought that was an interesting way to spell out what humans can and can't control.