Interesting to ponder. I am remembering the series of films 'Bandit' this and that and there engaging duo. I also reflected with Sally and the film with James Garner 'Murphy's Romance'. Seems may be an example aimed at the theme of the question? Other than films I have little knowledge of Burt and Sally.
I pondered the question with reflection. I realize I may have peculiar perspective with Love and lost? loves. To me Love is a Big Picture first and is presently relationship centric. Then, there are loves along the way. Perhaps that is with many or not? Even with a marital commitment or cohabitation there may be a lost love. Maybe not?
All those sets of experiences has measurable growth one way or another (IMHO) individually and combined. For instance I have friends who love much more the before 'spouse' while others the now spouse. I do not have that experience. The before spouse for me are the Long Term Relationships ending with departure for various reasons. So, lost loves.
With that perspective I feel kinda' each contributed to the present love I enjoy with joy again is relationship centric as Love. I still love my past loves while accept hers both contributing to Love. I hope she does too while believe she does.