What do you do when you love someone and they love you back but they are asking for a great sacrifice that you don't want to give to be with them?

I think if both people truly care about the other person's wellbeing, they would rather come to a compromise, rather than just expect one of the partners to make a sacrifice. (It would help to know what this person wants you to sacrifice.) This may mean both people agree to finding new jobs and moving to a new city halfway between where they each live, taking respective turns visiting each other when they're not busy with their educations or their jobs, or agreeing to raise any children they have with each of their religions. Things get much more difficult if you disagree on whether or not to get married or have any children--in that case, you will have to decide if a relationship with this person means more to you than a marriage or children.