the back-up plan

I'm one of those people who totes extra things around "just in case". I have a granola bar in my purse or backpack at all times, just in case I get hungry. I have a couple of hair ties around my wrist, just in case one or more of them breaks. And I bring along an extra layer with me if I'm going any place where the a/c may be cranked. I planned on wearing these pants with my mint gingham shirt, and stowed the sweater in my bag just in case I got cold in the library. On my way to campus, it started to rain. On my way to the library, the rain became a cold rain. Long story short, the sweater came in handy. Do you tote odds and ends along because you might find yourself...