More cheese, and a bit tongue in cheek given that this series is about reincarnation and both Nathan and Elena have had at least one lifetime as lovers with opposite genders to their current ones.
But I think this song does express the conflict they feel. They're meeting each other after decades apart, decades in which they've lived their own separate lives. How would you handle that? How would you cope with jealousy over other lovers from before you both found each other again? What about unresolved problems from your previous life? What if your lives have made you so different that you're not sure you can make it work in this lifetime?
Nathan and Elena may have been lovers before, but that doesn't mean the road ahead will be easy, or even all that clear. There are things they have done, and more choices to come, that they'll have to overcome if they stand a chance of being together again.