It's such a common term that everyone used th words, "If Only".
just like,
If only time could turn back,
If only i'd never did this,
If only i studied,
If only i rush to jiujiu house when we notice that's something wrong,
If only i born out earlier,
If only i never know you,
If only, if only, if only.
I observed that human behavior when something goes wrong is to say these words
"if only".