"Nothing is either good or bad, but thinking makes it so." This friendship that you're about to lose doesn't have to be a bad thing. It's a symbol of growth and maturity. It shows the world that you've found your path and it's not one to be shared. That's all. It's not you abandoning another soul or being uncompromising -- it's you doing what you're supposed to do.  Every experience and every relationship has value. However, some people are supposed to be part of our memories, not part of our destiny. And that's fine! It takes all kinds. Be thankful for the experiences you had because they let you grow. They made you the awesome person you are today. This friendship was turning you into a person you don't want to become (and yes, friendships have the power to do that). These toxic friendships can be draining and seep into other domains of your life. The only way to get around this is to slowly immerse yourself into a different group. A different group that makes you feel good.  If you don't have a Plan B, you will. You may have to find one. It'll be scary, but if it's too easy, it's not worth it. Join a club, take a class, pick up a new hobby. Allow yourself to become part of a bigger world. The bigger your world gets, the less influence this person has over you. When you're friends with a sponge, normally the sponge doesn't know they're being sponge-y. The last thing you want to do is lash out in a fit of anger -- after all, you were friends at a point for a reason. Some part of you cares for this person. When they ask you what's going on, be truthful, but kind.  If you're at a loss as to what to say, just tell them what you've been telling yourself. "We're on different paths and that's fine. I still value you as a person, but our friendship is based on the person I was, not the person I am. Your behavior brings me down and I don't want to be at the receiving end of it anymore." They'll have questions, and might get angry, but at the end of the day, you're better off regardless of their reaction. Sometimes...

TL;DR in Chinese:
尽可能地将事情处理得积极一些。 和其他人多在一起。 要友好。 和对方保持距离。 了解清楚你以后再找朋友的时候，看中什么样的品质。 只关注那些可以改变的。