Heard a Chinese student on the radio say,
“Forget the past and you will lose an eye. Dwell on the past and you will lose both eyes.”
Sounds like a good Chinese proverb, until I googled it and found:

A Russian proverb says, “Dwell on the past and you will lose an eye; forget the past and you will lose both eyes“.

Neither I feel is quite as satisfactory as Kung Fu, the TV series:
“If a man dwells on the past, then he robs the present. But if a man ignores the past, he may rob the future. The seeds of our destiny are nurtured by the roots of our past.”
http://scottishpaeds.org.uk/My%20Webpage/scribblings/kungfu.html