Buddha's analogy for discipline and laxity

Buddha had a good analogy. 

He said your life is like a vina (a guitar-like musical instrument). 

You must tune the strings just right: not too tight, not too loose. 

The strings being too tight would be equivalent to being too uncompromising, too strict with oneself.
The strings being too loose would be equivalent to being too lax: not disciplined enough.

You've got to tune the strings just right. Neither too tight nor too loose will work. 

The result is an in tune instrument.