You never bathe in the same river twice, do you?

a) Temporary marriages. As legal under Shia jurisdictions, but illegal in the West.
b) The unpredictability of the future cuts both ways. If you can regret having married, you can also regret not having married. (You can also regret having had sex, even if it didn't involve marriage, by the way). I have had my heart broken by many girls, but I will still love the one I have and the ones after her, like I didn't know I will be heartbroken one day, because it is completely worth it. I would regret more not having had them in my life.