I can't do it right now.
It can not be done at once.
It's impossible to go out now.
I can't let go now.
I'm not available right now.
I can't make it this time.
I'm not available right now.
We have no choice but to continue that.
〈万事休した〉 I can't go any further [do any more].
It's all over [up] with me.
We cannot live on it forever.
今回はしくじれないぞ。
We cannot avoid that.
It is no use struggling now.