In marriage counseling:
Usually, the treatment plan is for each of them to work on becoming their best selves, as well as on improving their interpersonal relationship.
I have studied with John Gottman, the leading researcher on the dissolution of marriage, who runs the "Love Lab" at the University of Washington in Seattle. I also like the ideas of Willard Harley, who wrote about the needs of husbands and wives, and what erodes the "love bank account" of spouses.
Spouses can learn to be irresistible, to love what they are giving and getting in their marriage, and to envision their Golden Anniversary as a wonderful example of a mature love and relationship for their friends and family.