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

Explanation

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.