What is the original text and explanation of the ancient poem "Although the tortoise is longevity"?

Although the tortoise is the birthday girl, there are still times when the tortoise is the birthday girl in the Three Kingdoms. The snake rides the fog and eventually turns to dust. The old horse crouches, aiming at thousands of miles; The martyrs were full of courage in their later years. The surplus and contraction period is not only in the sky; Blessings that nourish grace can last forever. I am glad to use this poem to express my inner desire.

Although the tortoise has a long life, it still has an end. Although poisonous snakes can fly in fog, they will eventually die and turn to dust. The old swift horse is lying in the stable, and its ambition is still to gallop thousands of miles. People with great ambitions will never stop working hard in their later years. The length of a person's life is not only determined by heaven, but also can be extended as long as he nurses his body and mind well. I am glad to use this poem to express my inner feelings.