I'm going to break it off with my fiance
do you want to break up with your fiance because you think you guys have grown apart?
I guess you are right. I don't have any reason for continuing our relationship
You guys should take the decision mutually. It's ok if you want to get out of your relationship if you think it's not working out.
I want to break up with her.
Then I think the best course of action would be to tell her the truth in person. That way you will have closure and she won't feel as hurt about the break up.