Get out of it as fast as you can or you will wake up one day wondering where your life went and why you were never really happy!!!

i'd pull the trigger and be outa there faster than a russian nuke headed for geoigia

There are other fish in the sea!

A couple I knew who had their 50th wedding anniversary and were very much in love told people at their renewal of their vows that the secret to a successful marriage was that they fell in love with each other over and over again. That there were times during a marriage when you did fall out of love with the partner and that the secret was to stick it out, work on the marriage together though those times, and you fell back in love with the partner again.

I'd probably smile and go, "that's nice."

Then I'd go outside and slash his tires.

But that's just me. Gotta love coping mechanisms (or lack thereof!)...

It would depend on how old and busted looking I was by that time.

Exit stage right...and fast.

Time to go.

walk. life is too short to stay where there is no love.

these boots were made for walking, and that's just what they'll do, one of these days these boots are gonna walk all over you.

Why waste your love in a relationship like that, everyone deserves better

I think I would first ask if they were joking. Since I can't imagine living with someone and not senseing that something was wrong I really would think he was playing a practical joke.
If he told me no he was serious think I would probably be in shock for a while and do nothing.
Then I would have to do some serious thinking. Observe the situation and see if there was a reason for them to have such a turn of the heart.
Are they ill mentally or physically? Stressed out by outside influenes? Some times depression or traumatic events can make a person numb to feeling love for anyone. As a RETIRED (no personal emails how to do I clean up this mess)social worker I have seen many people abandon spouses rather than tell them they were ill. I have seen crime victims (inparticularly sexual assault victims abandon partner's.
I think I would look around in our circle of reinds and see if the Big D was happening to anybody significant to my partner. "Divorce" of friends or siblings or parents can make people want to withdraw from their own "loving" relationships from fear or panic or even jealousy. Loss of a job puts a lot of people in panic mode. Illness of a child can drain people emotionally. I would have to decide wheather I just needed to practice my in sickness and health vow.
I think I would look around and see if someone was talking trash to my partner behind my back. I have an Ex sister in law that ran a number on my Ex telling him that because our child was the only one who was not blonde and blue eyed that he had to be someone elses. She looked like a chump when I had the genetic work up done. I have seen gossip destroy a lot of marriages.
I would have to assess if I have done something or "nothing" to affect their desire for me? It is real easy to neglect the ones you love when you have a lot of responsibilities. Grandma always said "you got to do what you did to get them; to keep them". You treat a spouse like one of the kids, or a co-worker, or a caregiver the romance tends to die out and love un tended withers just like a flower without food and sunlight. I think I would proably try re-prioritizeing my time and see if that helped.
Since I tend to put a lot of effort in a relationship I wouldn't necessarily want to throw in the towl immediately because of a "phase" I would give it a little time to see if it passed..
If I did a few special efforts and still didn't get any interest going I would probably ask for a family powwow. Nine times out of ten if someone says they don't love you they are trying to get your attention. If a serious heart to heart made it clear it was a conclusion and not a wake up call I think I would start planning my exit strategy.
I fully agree you can not make someone love you that has no interest. No sense watering a dead horse.
I do think I would have to really work hard at not being angry because I would expect a significant other to say something before it got to that point.