髀肉复生 — “To lament one's prolonged inactivity and lack of accomplishment”

After suffering a defeat at the hands of Cao Cao and losing his territory, Liu Bei sought refuge with Liu Biao, a member of the Han imperial clan. One day, Liu Biao invited Liu Bei for drinks and conversation. During their gathering, Liu Biao remarked to Liu Bei, "I regret not listening to your advice last time; we missed a great opportunity!" Liu Bei comforted him, saying, "The world is currently fractured, with battles happening every day. Just because we lost an opportunity last time, how do we know we won't encounter another in the future? Opportunities are endless. There's no need to regret what's already passed."

The two conversed congenially and discussed their future plans. A while later, Liu Bei excused himself to use the restroom. As he touched his thigh, he noticed that the flesh had grown soft and plump again. He couldn't help but shed tears.

Upon returning to his seat, tear stains were still visible on his face. Liu Biao, noticing this, asked him curiously, "What's wrong? Are you feeling unwell, or is something bothering you?" Liu Bei, feeling somewhat embarrassed, replied, "It's nothing, to be frank. In the past, I was constantly campaigning across the land, always in the saddle, and my thighs were lean and strong. But since coming here, five years have passed in a blink of an eye. Living in comfort and idleness, I haven't had to ride a horse, and the flesh on my thighs has grown back, becoming soft and flabby. Thinking about how quickly time flies and how I'm growing old without having achieved anything significant in restoring the Han dynasty, my heart feels incredibly heavy."