If one were in love to begin with, and then somethings happened to change the relationship...and one partner did fall away, I think if the partner who felt it happening and really wanted to put every effort into getting the relationship back on track... would do anything to "bring back that loving feeling" However it could take a take a long time, and just as in all things in life... there would be no guarantee that their efforts would be successful. It also has a lot to to do with "why they fell out of love to begin with..." somethings can be overcome, but not all.

Yes. Love isn't static. Plus feeling "in love" is different from loving and being loved. Even in stable, long term marriages and relationships, these feelings ebb and flow. It can be like a rollercoaster of sorts at times, too. Normal.