theres a first time for everything

Theres a first time for everything is an idiom which is spoken to refer to the fact that just because something has not yet been done or happened before does not mean it will never happen in the future. It is most commonly said after someone has denied that something exists or denied the possibility of something specific happening; by saying theres a first time for everything, you are given the hope that maybe you will be the one to see it happen for the very first time.