Worstest Kitty Ever

I feel horrible!!! Our neighbor came over with her puppy named Lotto. Even though I swore I'd be so nice the next time I saw him, I just couldn't help myself and hissed at him. He was very sweet and just looked at me and didn't get mad or anything. Feeling so bummed about this that I again did not meow with Tom Selleck. What's wrong with me?!!!