1. when one opportunity is lost, another may present itself
often when one door closes, another opens, so stay focused
This expression is often used as a means of consolation, when someone has experienced a disappointing outcome or a rejection, or things just didn't turn out the way they had expected. when you say 'when one door closes another door opens' it means although one opportunity or avenue is no longer viable another one will come along. By suggesting that another door opens, you are promising someone that another opportunity to achieve your goal or to be happy again will present itself. A religious version of this expression is, 'When God closes a door, he opens a window'.