I am going to let my ex know that we should probably spend some time not contacting one another.
Why don't you want to speak to your ex anymore?
I want to take some time to heal.
It's completely understandable to want some time to yourself to deal with a breakup, but you should also try to take your ex's feelings into account. They would be upset if you refuse to talk to them in the future.
I'm not trying to be mean, I just don't want to be friends with them anymore.
While you should think about your ex also when making this choice, sometimes you really do have to do what is best for yourself. You are the one living your own life, and if you think it would be better to not talk to your ex than that is your choice to make.