Last time I sent out my humble work, the afterword to "left-right", written on the promise that you'd keep it secret from him, this time it's the afterword to that afterword.
夜遅くまで起きていては駄目だよ。
Don't sit up late at night.
黙っていたほうがいい。彼に話しても無駄です。
You can save your breath. There is no use talking to him.
明日何が起こるかと心配するのは無駄なことだと思いませんか。
Don't you think it of no use worrying about what will happen tomorrow?