Don't Think and Drive!
Are you one who, at times, gets lost in thought? Long periods of thought are how we reminisce, or plan ahead and organize our lives. This is usually safe to do when sitting in your own home, or lounging on the beach or under a tree in the yard. It can even be safely done while pushing a cart down the aisle of a store, although that sometimes results in passing by friends or neighbors without seeing them, or perhaps in forgetting why you are in that particular store. But unless you run into someone with your cart, or inadvertently walk off with someone else's cart, thinking isn't usually dangerous.
Thinking while driving is another story. While thought is necessary for the safe operation of a motor vehicle, it is an "attention to everything around you" kind of thought. Planning a weekend dinner party or a vacation trip, or reminiscing about your last class reunion is not a good thing. That is the kind of thinking which causes drivers to miss seeing pedestrians in the crosswalk, or the flashing lights coming up behind because they missed the speed limit sign. It also causes some of us to drive several miles beyond our turn-off, at which time we turn around, hoping no one we know has seen us.
So be careful out there, and don't think deeply and drive. Save the heavy thought for when you're relaxing at home.