What keeps a relationship alive?

Why do some relationships flourish  and others fail.   What is it about certain relationships  that seem to strengthen over the years rather than wither.

My parents celebrated their 65th anniversary this year. My Dad is 90, my Mom 84.   They have been together since she was 19 and he was 25.   Their relationship is incredibly strong. They have weathered storms of  poverty, illness,  the deaths of their own parents  and many friends.   Yet they have remained best friends throughout.

I recently asked my mother what her secret was in the success of her relationship  with my father.   She told me that she always sees the glass as half full...  that life is filled with struggles but struggling alongside someone you care deeply about makes life better...  that second chances are earned through years of caring and devotion when missteps happen...  and that loving someone isn't just a word but a commitment to do the work.

I have great respect for both of them...  they have come through the storms of life without losing the lessons...   something I aspire to duplicate in my own life.