He's suffering from jet lag
시차 때문에 고생하고 있어

May: So， did you guys have a good time?
John: With James last night?
May: Yes， you said you were going to hang out with him at the Nashville. Did you drink a lot?
John: No， he decided to take a rain check because he's still suffering from jet lag.
May: That's right. He just came back from India. I forgot about that. What did he say about his trip? I'm sure India must have been a cool place to travel.
John: Actually， he said that he'd had really bad flu the whole time so he couldn't go around the county very much.
May: Oh， that's too bad. It's worst to be sick in a foreign

* hang out: <구어체에서> ~와(에서) 시간을 보내다， 어울리다
* rain check: 원래는 '우천 교환권' 또는 '물품 보증권'이라는 의미로， 우천시 옥외 경기가 중지 되었거나， 상품 재고가 떨어졌을 때 다음 번에 주겠다는 '유효표'를 말합니다. 여기에서는 '후일의 약속 또는 초대에 대한 연기' 등의 의미로 쓰였습니다.
* suffer from ~: ~로 고생하다， 어려움을 겪다
* no fun to do~: ~하는 것은 괴로운 일이다， 즐겁지 않은 일이다.
ex) It's no fun to be a graduate student. (대학원생이라는 것은 고달픈 일이다.)