不期而遇之时以笑相迎背道而驰之时以抱相拥
[bù qī ér yù zhī shí yĭ xiào xiāng yíng bèi dào ér chí zhī shí yĭ bào xiāng yōng]
This poetic expression means 'meeting unexpectedly with a smile, departing in opposite directions with an embrace.' It encapsulates the bittersweet nature of encountering and parting with people in life's journey, appreciating both reunion and goodbye.