Nothing is Sure except the Swing

Nothing is sure except one thing:
That stocks and shares will always swing.
Whether the trend is up or down,
The swing is always to be found.

Swinging high and swinging low,
Who can tell how far 'twill go?
Guided by what has gone before,
We guess old patterns will repeat once more.

Sometimes we're right; sometimes wrong:
One principle will guide us all along -
To limit the amount we risk,
So that profitable trades are larger hits.

We limit the risk by one device:
Quit quickly when we've not guessed right.
But hold on when it goes our way,
So that the trade will truly pay,

Watching out so we will surely spy
When the punt has gone awry.