"When I was younger and I was dating in my 20's, guys always say things to me to put me off… 'Let's just be friends', 'I'm not ready for a relationship right now.' 'You scare me.'"
Try it yourself. This is one of the easiest, most fun kinds of jokes you can create. Just make sure you when you say the first two things, that it doesn't sound like a list. Each list item should have the feeling that it stands on its own. That way, it'll actually be a surprise when you share the next thing, and the next thing.
Lists of 3 are great to spice up speeches and one-man or one-woman shows, too; they're not just for standup.