I thought everything would fall into place on its own. I think at 19 I wasn't really ready for what marriage entailed - that I would suddenly be an adult and have responsibilities.
I had a romantic view of marriage that we would spend our days gazing into each other's eyes and making love. And it was, frankly, a whole lot more work than I realized. It does take some adjustment, about a year to find a routine that suits you both. But we have lasted 42 years so it's all good.