spit and polish
When I was about 10 yrs old, we went to Montana to visit some cousins. They lived near an Indian reservation, and we spent a great week or two playing with our cousins and kids from the rez, horseback riding, swimming, lighting firecrackers, etc.
One day when we were all hanging around outside, my cousin Roxanne asked for a drink of my Coke. Roxanne was 14, and I had a huge crush on her. When I handed her my Coke, she took a big swig, and -- imagine this -- she didn't even wipe off the top first. My brother and I had spent all our lives scrubbing imaginary diseases off of whatever we shared before taking a sip -- and here was Roxanne just putting the bottle right to her lips, totally oblivious to the fact that it probably still had my spit on it. I found it incredibly sexy and cool.
Now, thirty years later, we're all married with kids and only see one another every few years; I'm a head taller than Roxanne is now, and I have normal cousin-ly feelings toward her instead of being smitten.
But I still remember that shared Coke – and from that moment on I dropped the wiping-the-bottle-with-my-shirttail routine. For the rest of my childhood* whenever I shared a drink with someone I took it as it was, spit and all, because it reminded me of Roxanne and her devil-may-care ways.
*some say this is still in progress