It always feels that way in the moment, like you’ll never get over them. But you can. And it’s true. You never know whom you’ll meet, when or where or how. It hurts now but that pain will lessen over time.
May I ask how you met him, how long you’ve known him and how it is that you two come into contact so frequently? It almost seems like you might work together since it’s so hard for you to ignore him and to distance yourself? If you see him more frequently by chance, then it’s harder.