Definition
This phrase is used to indicate that the opinion or statement someone has just made does not reflect your own view or experience.
"This movie was terrible." "Speak for yourself! I thought it was great."
"I think the food at this restaurant is mediocre." "Speak for yourself; I find the dishes to be quite delicious."
"I think this weekend was a complete waste of time." "Speak for yourself, I had a lot of fun."