The phrase "take a header" is a colloquial expression that means to take a sudden forward fall, usually with the head leading the way. The antonyms for this phrase would be to stay upright, remain steady or keep one's balance. These opposite actions can help prevent falling and injury. One should always try to maintain good posture, stable footing, and avoid risky behaviors that may lead to an accidental fall. Regular exercise and healthy habits, such as staying hydrated and getting enough rest, can also help improve balance and reduce the risk of taking a header.