A : Let's go for a drink after this seminar.
B : I'm afraid I can't.
A : Do you have any other plans?
B : No, I'm just feeling off today.
feel off 몸이 좋지 않다. 컨디션이 나쁘다.
= I feel blue, I feel under the weather
condition - 주거 / 작업 환경, 상황
I'm just feeling of today.