Why is romantic love so fleeting? (AI answer)

Romantic love is often fleeting because it is biologically driven by neurochemicals like dopamine and oxytocin that create an intense, addictive "high" during the honeymoon phase, which naturally diminishes after 1–3 years.  This initial passion is frequently confused with true love, leading to disillusionment when the intensity fades and the reality of a partner’s imperfections emerges. 

Psychologically, the collapse of ego boundaries and the projection of idealized images onto partners are temporary states that cannot be sustained long-term.  When these illusions dissolve, many individuals mistake the end of infatuation for the end of love, rather than recognizing the transition toward compassionate or companionate love, which is deeper, less volatile, and built on intentional choice rather than fleeting emotion.

Additionally, cultural narratives often glorify perpetual passion, creating unrealistic expectations that cause relationships to fail when they naturally evolve into a more stable, secure rhythm focused on shared life and mutual support rather than constant romantic intensity. 

Actually, agree with all this.  Deeper love is intentional choice, not just a feeling, though once you make that choice, feelings will often follow.