So what has happened? And what do you do about it?
1. Realize it could be you
It's possible that this feeling could be more about you than the other person. Maybe everything has lost its vibrancy. You could be getting more negative. It's possible you have become depressed. There's a symptom of depression called "anhedonia." All that means is that you don't take pleasure in previously pleasurable things.
Your partner could be one of those "things."
If this is the case, then trying to find ways to make your own life more invigorating, more productive or satisfying. Everything from biking to volunteering to making new friends. You might need professional treatment.
2. Be aware of how others are affecting you
A male patient one time said, "I can't find ONE trustworthy woman who doesn't want me for what I can do for her." (Interesting he chose a female therapist...) It was true he had been hurt, and badly, by a first wife who seemed particularly manipulative. But when I asked more questions, it seemed he mostly hung out with guys who talked about women very critically. And he tended to date women who were very needy - setting up the scenario he already believed.
Groups of women who bash men can be vicious. Men can be the same.
If everybody is grousing about relationship, it has an effect on you.
If these are the people you are hanging out with, your partner's light is just not going to keep shining. You are going to start picking them apart.
Choose to be with people who are happy in their relationship - that support you in yours. Chances are that things just might look up.
We have to live with the underbelly of our choice. Sometimes that is irritating, even disappointing. You don't "love" that part necessarily.
To stay "in love," you have to focus on the part you did fall in love with. Enjoy that part, relish that aspect of the relationship.
Realize that everyone has an underbelly.
4. Don't overreact to being out of sync. It's normal
Everybody's marriage gets "out of sync" sometimes. Your needs don't match up very well. Maybe a parent has died for one at the same time a huge job promotion with increased responsibilities has occurred for the other. Or a child is struggling with homework and falling grades, at the same time more money is needed for the roof that's leaking.
Who's going to give what? And when? We need something from our partner that it's tough for them to give.
Obviously if this is a chronic problem, we are talking about more than being "out of sync." Believing that your partner is not your enemy - isn't consciously trying to upset you or not be there for you - is vital.
You can talk about it. You can get the relationship back "in sync." It takes focusing on your own choices and being the healthiest person you can be. The other will often respond with like behavior - and feel a lot more lovable.
Dr. Margaret Rutherford is a clinical psychologist in Fayetteville, Arkansas. In 2012, she began blogging, focusing on mental health topics. Her work can be seen on The Huffington Post, The Good Men Project, Better After 50 and Readers Digest. She also has published one eBook, “Seven Commandments of Good Therapy.” You can listen to Dr. Rutherford on her podcast, SelfWork!