Seriously, many is the time I missed the nail - the head of that sucker is so small! - and brought the hammer down firmly on my thumb. If you've ever done this yourself, you know the experience is not a pleasant one. And once you've done it, the thumb becomes at best a reluctant recruit in further hammering activity. It goes along, yes, and takes its place beside the other fingers, but it does not do so with a glad heart. It hangs back. It cowers.
Trying to switch hands does no good. The hammered thumb is even more useless swinging a hammer than steadying a nail.
The rub is, that the thumb, which is the one object you're most likely to hit with a misfired hammer, is essential to the whole business. You never hit another part of your body which, while being painful, would not so incapacitate you. Your nose for example, is hanging out there in empty space, as tempting a target as ever there was, and yet it never gets hit, not once. "Tra-la-la," the nose says mockingly, "I don't see what you thumbs are complaining about. Hammers look perfectly safe to me."
I believe the same thing may apply to the human heart. In this metaphor, the heart will be the thumb and the world will be the hammer. When we are young, we put our innocent hearts out there, hopes and dreams, trust and belief, and blammo! The hammer of the world, sooner or later as hammers do, misses its intended target and crashes full force against our heart instead of hitting the nail which represents... Well, I don't know what the nail represents.
It does not take many such experiences for the average heart to grow fearful. This is not helped by nearby noses who laugh callously, "Tra-la-la, serves you right! What a chump!" (For the role of noses in this scenario, re-read the fourth paragraph.)
It is a terrible shame when the heart is cowed in this way because just as the thumb is needed to steady the nail, the heart is needed to steady the human soul. (How was that for a figure of speech? Pretty slick, huh? And you thought I'd lost control of the metaphor.)
Therefore, as you go out in the world, tap lightly. Consider your words before you speak - never "definitely" or "obviously" but always "maybe" and "perhaps." Be hopeful, yes, but humble too. Be grateful but take nothing for granted, so when the hammer falls, it won't fall so hard. And if you find yourself a nose, an unscathed witness to someone else's misfortune, don't be smug. Your turn to be the thumb is coming soon enough.