If heaven had feelings, heaven too would grow old; the true path in the human world is one of vast vicissitude.
Tips
history
Originally from Li He's (李贺, mid-Tang) 《金铜仙人辞汉歌》: 衰兰送客咸阳道,天若有情天亦老 — 'Withering orchids see off the traveler on the Xianyang road; if heaven had feelings, heaven too would grow old.' Later given new life by Mao Zedong (毛泽东) in 《七律·人民解放军占领南京》: 天若有情天亦老,人间正道是沧桑 — Mao's couplet is what most modern readers know.
usage
Today usually quoted in Mao's pairing with 人间正道是沧桑 ('the true path in the human world is one of vast change'). In Li He's original the counter-line is different.