To keep a relationship flourishing:
Talk about things, the good and bad.
Be there for one another.
Make time for one another.
Leave the past to the past, which include ex´s.
Know that having arguments is normal.
Know that you won´t always be happy.
Don´t expect the other to change.
Appreciate the flaws.
Appreciate each other.
Become best friends.
Lastly, love each other unconditionally.