Sink in the river
The lessons I learned
It like, money went against the song writer of this particular song. What I mean is, maybe someone, a close friend was given money to go against the song writer. So he says "sink in the river, the lessons are learnt" meaning, "don't go against people just for money. Keep it as far away from you as possible, see what it has caused! Such a disaster!" not necessarily money! Anything that anyone has used to go against you with!