笑道心疼
[xiào dào xīn téng]
It implies 'heartache even while smiling'. In daily life, this phrase can reflect inner pain or uneasiness hidden behind laughter, which is often used to describe situations where a smile hides deep sorrow. Such a username suggests the user may have learned how to face difficulties and pain in life with resilience, turning them into something they can smile about on the surface while bearing pain within themselves.