How Does the Hippocampus Know, Oh, This Must Be Important?

We only have this storage cabinet in our brains that is limited. So how does the hippocampus know, oh, I'm going to hold that one? What am I going to put into long-term memory? Or what is going to, I don't need to remember what I have for breakfast. Unless it was amazing. If you get a shot of norepinephrine cortisol, if you get that adrenaline shot, that usually tells the hippocampus, Oh, this is important.