始于心疼止于心累
[shĭ yú xīn téng zhĭ yú xīn lĕi]
Translated directly as 'Started from heartache, ended in exhaustion'. It indicates that the experience of falling out of love, starting from the pain one's affection caused, to the point where emotional effort becomes draining. A journey from deep caring to complete weariness and dispassion.