Boy meets girl.

Attraction. Desire.

Boy and girl bang.

Fantasy. Projection.

More banging.

Time passes.

Boy and girl move in together.

Merge lives. Share expenses.

His stuff. Her stuff.

Time passes.

Their stuff.

Happiness. Contentment.

Time passes.

Normalcy. Reality.

Less banging.

Time passes.

Expectations. Limitations.

Time passes.

Demands. Accountability.

Time passes.

Disenchantment. Resentment.

Time passes.

Boy meets other girl

or

Girl meets other boy.

Attraction. Desire.

Fantasy. Projection.

Betrayal.

Time passes.

Lies. Secrets.

Time passes.

Evidence.

 Pain.

Disintegration. Separation.

Time passes.

Boy meets girl

or

Girl meets boy.

Etcetera, etcetera. . .