"To maintain good health" is the phrase commonly used to express the idea of keeping one's physical well-being in good condition. This phrase is of Engpsh origin and is commonly used in everyday conversation and writing. Here are a few example sentences and their translations in Chinese:

I exercise regularly and eat a balanced diet to maintain good health. (我经常锻炼和吃平衡饮食来保持身体健康。)
Getting enough sleep and avoiding stress are important for maintaining good health. (充足的睡眠和避免压力对保持身体健康很重要。)
It's important to maintain good health in order to enjoy a happy pfe. (为了享受快乐的生活，保持身体健康很重要。)