It's not easy, especially if you really care about the person. But sometimes you really just have to think about what's best for YOU. It'll be an adjustment and hard as hell but in the end I promise it'll be better for you. Don't just ignore the person though, you don't want to make them feel like shit. Make sure you let them know how you feel and make it known to them that you're not interested in the friendship/relationship anymore.... Or you might just naturally grow apart. That's less painful without a doubt but idk it's up to you. Hope that helped at least a little