The fickle, unsteady mind, so hard to guard, so hard to control, the wise man straightens, as the fletcher the arrow.
Dhammapada 3 : 33
When will we 'mind our monkey mind' ... a mind weakened by sensual pursuits, restlessness, aversion, anger, illwill, mental laziness, confusion and ignorance.
A person would have lived his life well if he continually trains the mind through practising all the factors of the Noble 8-Fold Path. With a mind rid of the 'devils' of greed, hatred and delusion, he eventually crosses the 'Sea of Samsara.'