Break up to make up

I have a genuine question that may apply to some of you ladies. Why have you and your partner broken up and later down the line (let’s say months later/ year) got back together.

Is it better now? Did it fail?

I have a cousin who was with his gf for a couple of years and they broke up for a year and are back together. I asked him and he said even though they argued so much he knew she was the one, it took him not having her to realize.

He said once they got back together it’s never been better, they don’t argue as much anymore now since he knows she’s the one he’s changed and just wants to be happy with her.