A mind not to be changed by place or time.
The mind is its own place, and in itself
Can make a heav'n of hell, a hell of heav'n.
Source: Paradise Lost, Bk i. 253.
-- John Milton, (Dec 9 1608-1674), English poet, essayist; He was a master epic poetry; Wrote in four languages including Paradise Lost, 1676, after losing his sight.