Do you have familiar markers on your morning commute that let you know you're on time? If I'm on my way to work and I pass the woman who leaves a trail of Theirry Mugler's Angel perfume behind her near the top of the hill, I know I'm doing ok. If she's down the bottom of the hill already, I know I'd better start running.
And if I pass this guy in his garden? Then I'll be there bang on 8.00...as long as I don't stop to take photos!