Appreciation
Appreciate and do everything possible to keep who you have while you still have him/her. Don't lose who you have before you start knowing the value. If you do, that person you once had that you never appreciated will become one of your utmost desires that you may NEVER have again.
Imagine yourself wishing to have who you have lost, when that thing was once all yours?
The best time to appreciate and keep that person with words and acts of gratitude is NOW! Tomorrow may be too late.