In some cases you have to walk away maybe for your own self respect or dignity.
When someone walks out of your life, let them. There's no use in wasting your time on people that leave you. What you make of yourself and your future is no longer tied to them. Yeah, you may miss them. But remember that you weren't the one that gave up.
Leave your past and be ready for your future.
If you love life, don't waste time, for time is what life is made up of. ~ Bruce Lee
We waste time looking for the perfect lover, instead of creating the perfect love. ~ Tom Robbins