My great grandmother always use to tell me (my grandmother and mother both divorced and the 3 generations of women raised me and my brothers)
Falling in love is easy, staying in love is difficult. To stay in love you have to choose to love someone even when you don't like them. You choose to love who they were, who they are and who they will become.
She was a widow for 5 decades after her husband died at 62 and I honestly belive that her love for him was the only thing that allowed her to live life for so long on her own.