When do you know s/he is the one ??

A question for all boys and girls. I want to know when does a guy know that she is the one ? Or a girl locks in saying i am gonna be with him?

Or it it always fluctuating ?

Like huncha ni guys haru ko man ma aauni yes she is the one she will stay no matter what bhanera or girls lai i will stay with him, he is the one bhanera ?Like kunai trait habit action le dekhaucha ki something else ?

Kunai hardship ma sangai basnu or something private k hola ?

( Only mature answers please no jokes ) .