You may feel your partner doesn't really know you anymore, and you may not really know your partner. If this sounds familiar you may want to intervene NOW! Don't let more distance come between you!
Try adopting an attitude of CURIOSITY! What do I mean by that? Start WONDERING about your partner. Does s/he feel loved? What was her/his day like? What does my partner need from me right now?
I love those words: WONDER and CURIOSITY. Those feelings come naturally when we begin a new relationship. Just because you've been together for 5 or 10 years doesn't mean you know everything about your partner. Try to see him/her with fresh eyes, and get curious!