(I think this one is especially good)
Love is a choice, not a feeling. It is an initiated action, not a knee jerk reaction. Choose today to be committed to love even if your spouse has lost most of his (her) interest in receiving it. Say to him (her) today in words similar to these, "I love you. Period. I choose to love you even if you don't [seem to] love me in return."
I especially like this one because it is so different than what the world tells us. Real love is not something we fall into. It's something we choose. It's an action. I've always felt distinctly that nothing will make more of a difference in my marriage than the effort I choose to put into it. Even though this requires more of me, it also gives me a continual sense of empowerment. I can make a difference.