People are alone when they are born and they are alone when they die.
You're born into this world by yourself and leave this world by yourself.
この場合、次のような言い方ができますよ。
ーPeople are alone when they are born and they are alone when they die.
「人は生まれた時も死ぬ時も一人きりだ」
alone「一人で」を使って表現できます。
ーYou're born into this world by yourself and leave this world by yourself.
「人は一人でこの世に生まれ、一人でこの世を去る」
by yourself「あなた一人で」を使っても表現できます。
ご参考まで！
カナダ 
