How to?

How do you stop caring about somebody that you love, are in love with .. Would do any and everything for .. Would hand them the entire world if you could .. Who you forever seem to think about and who always crosses your mind .. Who you thought & gave you ever reason to smile ... Who you share a child with ... How do you just forget about them and move on with your life? How do you let go since they don't feel the same way about you anymore ... How can I get over him? Somebody please tell me how because right now I feel like I'm dying inside ..