The Buddha told a parable about a man who was traveling on foot and came to the bank of a wide river.  The only way the man would be able to move forward on his travels would be to cross the river.  So he gathered what was around him--branches and logs and leaves and vines--and built a raft.  He pushed the raft into the water, lay on his stomach on it, and paddled with his hands and feet.  It worked.  The raft got him safely to the other side of the river.  But then, instead of leaving the raft behind now that it had done its job, the man hoisted it onto his back and began carrying it.  And so, the thing which had previously enabled him to move forward now became a burden which impeded his progress, because he couldn't recognize that it was time to let it go.

-DC