It never occurred to me that I would regret doing that one day in my life.意思是:在我生命中的某一天我会遗憾我做了那件事的情况绝对不会发生。It形式主语; never occurred谓语; to me宾语; that引导宾语补语从句; I 从句的主语;would regret 从句谓语,doing that从句的宾语 one day in my life.状语。
在我的生命里,我永远不会后悔我所做的那件事情。