“I can’t go out with you this weekend, I’m busy [worrying about what going out entails in your mind].”
“I’m not really looking for anything like that right now [or ever].”
“I think we’re better off as friends [because I like you too much for anything else].”
“I don’t want to waste your time [because that’s how you’ll see it].”
“I understand what you’re looking for and I know it’s not me [I wish it was], but I really hope you find it.”
“You’re such a fantastic person [I just can’t].”
“I’m just not into you [anyone] like that.”

Sorry [about what could have been – but trying to be less sorry for who I am].