It's good to swap with people.
Reba is at lunch and Jack has asked her to swap half of her sandwich for his.
Reba wants to enjoy her lunch.
Reba swaps half of her sandwich with Jack and finds his sandwich surprisingly good.
Reba refuses to swap with Jack because she does not think his sandwich will be very good.
Jack enjoys his lunch with Reba and is pleased she shared with him.
Jack's feelings are hurt, and he does not think Reba likes him.