‘Don’t cross the bridge before you come to it’ is an idiom. It means that we should not worry too much about future problems. Whenever a proposal is made some people have a tendency to imagine all kinds of difficulties. This idiom means that we should deal with problems as and when they arise. We should not worry about them too much in advance. We should deal with them if and when they occur. We should not worry about them unnecessarily. This is the meaning of
‘Don’t cross the bridge before you come to it’ You can also say ‘Don’t cross your bridges till you come to them!’”