This relationship is over. I will tell you "let's take a break" because it seems like there is a chance that everything will work out, but I don't want to be with you, so that won't happen. This is often used in conjunction with several lies to make the other person "feel better" about the situation.
"Maybe we should just take a break"
"Don't worry, I'm sure everything will be fine, I just need some space and time to figure things out"
"Are you dumping me?"
"No way, you're my girl!" (Lie)
"Of course..." (Lie)