expression
no one knows what the future holds; the future is a closed book
Proverb emphasizing the unpredictability of the future; literally 'one sun ahead is darkness'.
一寸先は闇だから、明日のことを心配しても仕方がない。
Since no one knows what the future holds, there's no point worrying about tomorrow.
A traditional Japanese proverb. The literal meaning is 'one sun ahead is darkness', where 一寸 (いっすん) is an old unit of length (about 3 cm), implying that even a tiny step into the future is completely unknown.