I am curious about how do you usually recover your energy when you are knackered.
If you don't have lots of time and you have to do many things.
HyunJu, do you realise that 'knackered' is a slightly crude and vulgar expression, exclusive to British English, and only used in very informal conversational contexts among friends?
Seeing a nice, well brought up Korean girl using it in a piece of writing on a public forum is, well ...unusual, not to say inappropriate. You might want to replace this word with an expression which is (a) more polite and (b) more accessible to the rest of the English-speaking world.
I just would go to bed when I was really tired! If I had a bit every to do something, I would talk my frineds, reading books, or studying English!
I've heard that talking or hugging with people you feel comfortable being with release your stress a lot psychologically!