walk the line

verb

a) To maintain an intermediate position between contrasting choices, opinions, etc.

I sat at dinner, but satisfied myself with nibbling bread crusts, and witnessing the forlorn and perilous efforts of my friends to walk the line between starvation and acute indigestion.

b) To behave in an authorized or socially accepted manner, especially as prescribed by law or morality; to exercise self-control.

I began to walk the line between work and play.

See Also: toe the line