Dating help?

I am actively dating. I usually know after the first date and definitely by the second date if I don’t want to see him again. They are all nice gentlemen and I want to be as kind as possible. I have used some cheesy lines such as, “You are a great catch but not for me.” Also, “I am not feeling the personality connection.” As I type these they sound so lame. Anyone have any suggestions. I searched the boards here but could not find anything. Be kind and thanks.