How do you make a relationship better?

Depends on the set backs and what's lacking in the relationship. If sex is lacking, spice it up with hot lingerie, toys, candlelight dinners, etc. If fun/playing is a set back, go places that are mutually fun like a sports game, amusement park, funny movies, etc. to laugh with each other. If the relationship is just stagnant, start doing one new thing a week and avoid the "come-home-sit-and-watch-TV-go-to-bed" cycle.