ORSINA: Better counsel comes overnight.
[Besserer Rat kommt über Nacht.]

Gotthold Lessing (1729-1781) German playwright, philosopher, dramaturg, writer
Emilia Galotti, Act 4, sc. 3 (1772)

It is unclear if this is a traditional German saying, or was coined by Lessing. There are parallels in other languages (as well as German), but I did not find a German reference in these words that predates this play.

(Source (German))

Better counsel comes with the night.
[Source (1842)]

Morning brings better counsel.
[tr. Lewes/Taylor (1890)]

Better counsel often comes by night.
[tr. Gode-von Aesch (1959?)]