What convinces is conviction. Believe in the argument you're advancing. If you don't you're as good as dead. The other person will sense that something isn't there, and no chain of reasoning, no matter how logical or elegant or brilliant, will win your case for you.
“If you serve well, your volleys are going to be so much easier. It has got to do with confidence, obviously.”
“Animals keep you company when you're really lonely. It helps because when you have a friend around who always likes you no matter what - it's harder to feel bad or down.”