Ours is a culture that wants to go directly from A to Z with no waiting or sweat in between. But on a deep level we all know that every path is made up of many steps, taken over time.
Invite couples to talk together and to make a joint decision to work on their marriage and increase their relational stamina. You could say it this way:
Create a goal for the two of you. It could be to spend fifteen minutes a day walking together. The effort you give to your physical muscles is a good parallel to increasing the strength and circulation in your marriage too. Some people skip the talking and just share an ipod with favorite music and one set of earplugs. Hold hands, not necessarily because you are already feeling affectionate, but as an invitation to those feelings to return. It could be to smile more often, or hug a little longer. Perhaps it will be to spend time doing something you both enjoy, but have forgotten to remember.
Notice that it may be hard to get started, or to keep going. Have a plan for getting over those bumps. You could write little encouraging messages to each other, to stuff in your pockets and take out when you need them. You could bring yummy things to offer to each other on the way.
Then come back as a whole group to talk about it.