老骥伏枥lǎo jì fú lì

三国魏·曹操《步出夏门行》：“老骥伏枥，志在千里。烈士暮年，壮心不已。”(烈士：有志功业的人)比喻年已老但雄心壮志不减当年。

英able men tied down to a routine post; ambition survives even in old age like the old steed in the stable that still wants to gallop a thousand li;