Once upon a time there was a clam that grew a beautiful shell. The two halves of the shell were perfectly matched to each other and were very, very happy together.
Most people don't realize that the clam's shell is the smart part. The clam itself is just a dumb mollusc. But to realize its full potential, the two halves of the shell must work together, and the clam helps with this.
So when the clam died, as clams always do, the two halves of the shell were concerned -- with good reason, because it wasn't long before a big wave jammed the male half into the sand and tore loose the female half. When the sand washed away from the male half, its partner was nowhere to be seen.
For years the male half drifted back and forth, back and forth in the waves, wondering if he would ever see his other half again. The sand wore away his youthful sheen and his edges were chipped on rocks, but ever time another shell washed by he would ask, "Are you my other half?" Sometimes they would be almost right, but there was always some difference in size or shape that made them incompatible.
Then one day another shell half washed up beside him that looked just right. He asked, "Are you my other half?" His other half recognized him immediately, although both of them looked a lot different after all the years of abrasion and abuse. But she knew that he would expect her to be just as he remembered, and too many waves had washed over them both for that to work, so she just said,
"No, but we're a pretty good fit."