Une chose très naturelle

When David, an ex-monk still in his twenties meets Mark, he falls hard; soon he's asked Mark if they can live together. Things go well for awhile, and then differences in their definition of "commitment" begin to push them apart. Mark wants other sexual adventures, David tries to go along. Can they talk through the crisis in their relationship or is a breakup in the offing? David sees his relationship with Mark as a marriage, so if it ends, can David's heart ever heal?