A man was being carried along by the flow of a river...

"Suppose a man was being carried along by the flow of a river, lovely & alluring. And then another man with good eyesight, standing on the bank, on seeing him would say: 'My good man, even though you are being carried along by the flow of a river, lovely & alluring, further down from here is a pool with waves & whirlpools, with monsters & demons. On reaching that pool you will suffer death or death-like pain.' Then the first man, on hearing the words of the second man, would make an effort with his hands & feet to go against the flow.

The meaning is this: the flow of the river stands for craving. Lovely & alluring stands for the six internal sense-media. The pool further down stands for the five lower fetters. The waves stand for anger & distress. The whirlpools stand for the five strings of sensuality. The monsters & demons stand for the opposite sex. Against the flow stands for renunciation. Making an effort with hands & feet stands for the arousing of persistence. The man with good eyesight standing on the bank stands for the Tathagata, worthy & rightly self-awakened."

Even if it's with pain,
you should abandon
sensual desires
if you aspire
to future safety from bondage.
Alert,
with a mind well-released,
touch release now here,
now there.
An attainer-of-wisdom,
having fulfilled the holy life,
is said to have gone
to the end of the world, gone
beyond.

Iti 4.10; Iti 114