At a friend's funeral I understood this for myself: The only "right" time to do something is now. If you wait until the moment is "right" it'll never happen, because you'll spend forever waiting for that time to come. The only right time to say "I love you" is now. If you wait until tomorrow your friend might not be here anymore, or things may have already completely changed.
My friend died out of the blue this New Years. No chance for goodbyes, no chance to say I cared.
It's not easy because saying "I love you" is about vulnerability. I think Brene Brown explains it best.