not too tight and not too loose

"Once when the Buddha was asked about the optimal way to be, he answered, using the analogy of a stringed instrument, 'Not too tight and not too loose.' Even the Buddha could not define or formulate this state; he could only say what it was not, and invite his questioner to find it for himself." - John Welwood. "Journey of the Heart: The Path of Conscious Love." HarperPerennial, 1996