Choices
Choices are strange things. Sometimes you don't think you have a choice, only to realize later that you did, and that maybe you made the wrong one.
That was how Agnon felt about escaping from Tartarus. At the time, he'd been desperate to leave, so when Cronus offered him the opportunity, he took it. Later, however, he came to regret his decision. By the time that happened though, it was too late to do anything about it. He couldn't just run away. He didn't have anywhere to go.
It's hard when you have two choices and both are equally bad.