One single slip brings eternal regret, and looking back, your whole life has passed away.

一失足成千古恨，再回头已过百年身。

《新英汉大辞典》

He shakes his head at the thought of this one thing, this single hideous bead on the necklace of his life.

他一边思索着这件事一边摇着他的头，他生活的项链上唯独可怕的一颗珠子。

youdao

The death of a single human is a tragedy, one that survivors sometimes never recover from, and we prize the individual life above all.

每个人类个体的死亡都是一个悲剧，逝者已矣，生者有时却永难释怀；而且，我们认为人的生命高于一切。

youdao

Forever convinced of her own innocence, Catherine declares that one loves truly only for a single moment in life.

WSJ: Jules and Jim | For the Love of a Fickle Woman | Masterpiece by Peter Cowie

He needs every single one of you to give just a little part of your life each week to this campaign.

WHITEHOUSE: REMARKS BY THE PRESIDENT AND FIRST LADY AT A CAMPAIGN EVENT

Single-issues groups often tend to see all spheres of life including the judicial one as subordinated to the truth they preach.

CENTERFORSECURITYPOLICY: Center For Security Policy