Lu Shang didn't spend any more time on the cliff, he directly went home after gaining an insight into the wind withering technique. This was already enough for him if that was the only thing he was able to accomplish today, it was okay and he was extremely tired because he was mentally drained after pondering heavily on the wind energy.
If he was physically tired it would have been good but it happened to be his mental health that was drained, mental health and physical health can't be compared. Except for relaxing his head to regain himself, there was nothing he could do in fully recovering his mental health unlike his physical body which he can cultivate and he will be able to fully replenish his energy and then continue with what he was doing.
