Struggling

For the last few weeks I have been struggling with something and I thought I would ask you all what you do when you need to let go of a person, someone you love very much. How do you do it? How do you stop loving someone? Or is letting go different than not loving? I can easily put a stop to negative thoughts and even not thinking about this person, but then wham I am thinking of them and when I do I feel sad. I know I am not the first who has had to deal with this, so if any of you have some sure fire remedy please share :-). Thanks.