I have this headcanon where Percy and Annabeth are NOT okay after the war.
In the beginning they are just like, so depend on each other and have nightmares and it's become known fact to never wake them up because you may end up dead before they'll even realize what they're doing. And the only one that could comport them is each other.
And very quickly Annabeth moved to Poseidon cabin and of course no one said a word, especially after couple of people heard them comforting each other. Percy would tell Annabeth over and over again that "it's okay, we're together" and he won't stop saying that until she fell asleep but the worse thing was Annabeth comporting Percy because she only said two words: "I'm okay". And this was the only thing that could make Percy calm down.
But then, they got better. They started to talk again, eat regularly and train with everybody. It looked like things are getting better. But then Percy would try to protect Annabeth when something he knows hurts her comes up in and she gets mad. She screams that she's not a damsel in distress and she doesn't need Percy to protect her. She doesn't mean that but having someone protecting her makes her feel vulnerable. She Apologized later and Percy pretend that he doesn't care but she really hurt him.
Annabeth try to pretend that everything is back to normal and make a "stupid Percy" joke. He doesn't find it funny. After everything he's been through he isn't the same childish Percy and it's not okay that Annabeth doesn't get it.
They drift apart slowly.
Annabeth decide to go back to her father's house and school. Percy tries to do the same for a while but he fails miserably. He decides to give up on the idea of high school. His mom is disappointed, not because of the studies, she herself, after all, didn't finish high school, because she still want Percy to have happy, normal life. She still support him though when he decide to go some kind of a road trip, even if it breaks her heart letting him go.
Percy had enough quests for a seven lifetimes and there is nothing he wants more than stay in one place from now on but he just can't. After traveling (if you can call it "travel") for so long it's just impossible to stay in one place. He starts to travel all over the country, killing monsters, helping demigods and never looking back. He meets his friends from time to time. He runs into the hunters occasionally and he speaks shortly with Thalia about camp. They always say little because the rest of her hunter doesn't want him there. They never say a word about Annabeth.
Sometimes Percy runs into satires in schools or the wild and he has a feeling that they tell everything he told them to Grover and for some reason it makes him feel a bit better.
Sometimes Percy thinks this will be his life until he dies but then he run into a familiar monster. Kelli. The very same Empousa Annabeth killed in the labyrinth and they later met in Tartarus. And suddenly, he can't stop looking back. Suddenly, everything reminds him of Annabeth and their adventures.
Percy didn't start his journey with much. Usually he lives on stolen food, hospitality of fellow demigods, gifts from satires or nature spirits and spoils from his battles. That's the reason he doesn't have and drachma to IM Annabeth. First he decide to wait until he gets one but he understands very well that if he want talk to Annabeth now, he'll never do it.
Eventually he finds enough coins (which are pretty easy to find compare to drachmas) and a payphone (who knew these things still exist?) and calls her cell. He half expect to find out that she changed number but her voice mail is very clear. "This is Annabeth Chase' Phone. I can't answer now. Please leave a massage". That's it, nothing funny. He's not sure if it's good or bad. He almost hangs up the phone but he stops himself at last.
"Alright," he says out loud. "Hi Annabeth… This is Percy. I just… I don't know. I have no idea what you're doing now but I hope you enjoy it. I'm just… I'm lost, Wise Girl. I'm tired and I miss you. I know it's a bit too late for all of this but I just wanted you to know that and… I don't know. It's not what I thought will happened when I told you I have a plan for us. Remember that? You told me I'll tell you everything when we'd get out. That never happened, huh? Forget about it. It was stupid." He doesn't say anything for few seconds. "Bye." And he hangs up.
Life's back on track for few weeks. He wanders from one town to another, kills monsters, try to help demigods he meet on the road and try to forget.
And then, one night, he wakes up from another nightmare but this time it's different.
"It's alright." He hears a familiar voice say. "I'm fine."
He opens up his eyes to see the shimmer of an Iris message in front of him and in the other end of the line he sees a beautiful woman. Her Blonde looks dirty and her grey eyes are teary but she still looks perfect.
"I'm okay, Seaweed Brain," she says softly, "We're okay."