Woman to Woman

We've all been through heartache and we all know it sucks. I'm in love with the man Im with but I can tell he no longer loves me and the pain I'm putting myself through is beginning to be unbearable. I can not make him love me, I can not make him see me the way he use to. My question to you ladies is simply.. How do I leave? How do I walk out on a man I am completely in love with? I know it's what's best but leaving sounds so hard and I don't know what to do. My mind is going crazy and I'm at a loss. I need advice.