I need help with this: If I don’t think about my neighbor I think about death and ppl I love dying and so I think about my neighbor except i know I’ve

Thought about my neighbor everyday for the passed 10years and that sounds crazy. And I don’t want to think about them bc they’re never gonna be anything more than just my neighbor, but when I decide not to think about them my brain goes to death or negative thoughts. Thinking about my neighbor keeps me positive but I need to move on I can’t keep thinking about them for the rest of my life. Are there any mental exercises I could do to untrain my brain from thinking about them and then also automatically go to thoughts about death???