After you enter the age of 30, the top priority is to learn how to make choices. If you continue to indulge yourself and still indulge in pleasures like when you were 20, then you will grow into a lump of meat. If you insist on having your own way, when you are 40 or 50, you are very likely to become a bad-tempered monster and be surrounded by diseases. There is a way to keep fit after the age of 30, that is walking.