365 reasons why I love you jar. Both have their own jar and write once a day one thing they love about the other. On their anniversary/birthday/valentine's day/christmas/whatever the occasion, open the jar and read what the other person wrote
Remember: Doing Nice Things for your family is just as good as for strangers. Don't tell them about it- just leave it for them to find. A sweet loving message or a thank you or an encouragement. Any kind word is good. The Art of the Surprise Note .