How many relationships have you been in before you were able to build a successful one?

I guess I’m mostly targeting this question and would like to hear from married couples. But anyone else is welcome to share if it seems relevant.

How old were you when you had your first romantic relationship, and how long did it last? How many more relationships did you have before you found someone you wanted to spend the rest of your life with and built a successful relationship? And how was this relationship different than the ones that did not last?

I’ve seen a lot of high school sweethearts who were together for 6 years, but then broke it off. People can date numerous amounts of people with no luck, but some have built a successful relationship from their first. So, how about you? How did you build a successful relationship and was it different than the rest?