Leo had never been jealous of someone, really, until he met Jason Grace.

Jason seemed to have everything a girl like Piper could want. He was handsome, a good leader, son of Zeus, of all gods, and was respectable and powerful, only to name a few qualities that made girls drool over him.

Every time Jason said something sweet about Piper, or Piper commented about something she liked about Jason, maybe his perfect blonde hair or how brave he was, Leo couldn't help but think: why isn't that guy me? The person who every girl always wants to be with without even meeting in person?

Sometimes Leo would lie awake at night in his cabin on the Argo II. He'd tell himself that he was overcome with the stressful burden of fighting monsters, or one of the many pressures between the seven. But he knew inside he was just staring up at the ceiling and hating someone who was once his quest partner and best friend.

When he did that, he felt a pang of guilt, like, I shouldn't feel this way.

But he did. He did, and couldn't just stop it with the push of a button.

Sometimes, when Jason and he were talking, he'd accidentally say something along the lines of, "Well, no, it won't happen to me, you're the one with all the luck."

Jason just ignored those comments. Good thing. If he didn't he could think that Leo was self-absorbed or jealous.

Maybe he was. Leo just didn't want anyone to know, of course.

Jason had secrets.

Sometimes he wished he was more like Leo. The person who always had high spirits no matter how low the situation. Who had braved horrible things and came out with, of all good qualities, a sense of humor.

No, being brave won't cut it. Attitude is almost everything when you're on the Argo II.

And Jason did not have the best attitude all the time.

Of course, he wasn't faking his relationship with Piper. And he was friends with Leo. He liked having them as quest members.

But, sometimes he'd think: "Why was I even chosen for this quest when everyone else can do better than me? All I do is summon lighting to burn up our boat; I'm not even such a good fighter!"

Jealousy won't get either of them anywhere. They knew it. But they were jealous of each other, and wished they were different people.

Jealousy can lead to a bad mistake.

In this case, it certainly did.