How to Nicely End a Long Distance Relationship After a Breakup

there's unfortunately no 'real' nice way to say it than to tell the truth. it's most likely going to hurt you, and him, but if it's the step you want to take then take it with your heart with you

Hey! That’s a sucky position to be in, I’m sorry you have to deal with that. Maybe try sitting down with him and explaining to him that you are no longer interested in being in a relationship and that you need time alone. Tell him that there is nothing he can do to change your mind and that you think he is a wonderful person and all that jazz. If you are all he has that is unhealthy on his part, and not your fault so you shouldn’t feel obligated to be the only one there for him.