You should pray as long as you have the energy to do so. If you feel tired, then lie down

Anas (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) came one day into the mosque and saw a rope stretched between two poles. He inquired: "What is this rope for?" He was told: "This is Zaynab's rope. When she feels tired (in voluntary prayer), she holds on to it for support." The Prophet (may Allah's peace and blessings be upon him) said: "Untie it. You should pray as long as you have the energy to do so. If you feel tired, then lie down."

The Prophet (may Allah's peace and blessings be upon him) entered the mosque and saw a rope tied between two poles. He was surprised at that and asked why the rope was tied like that. The Companions (may Allah be pleased with him) answered that the rope belonged to Zaynab bint Jahsh (may Allah be pleased with her). She would pray lengthy voluntary prayers, and when she felt tired, she would continue to pray while holding on to the rope.

He ordered them to remove the rope and instructed them to be moderate in worship without going to extremes and overburdening themselves so that they perform worship with energy and vitality.