Explain why the process of balance is possible in the human body?

Why are you asking about "possible"? That makes no sense. What you want is an explanation of how balance is maintained. That is a very intricate process. The joins have reflexes to maintain balance without any thought at all. The ear has a fluid cell to detect motion. That is what makes you dizzy when you turn. You will need to do a lot of studying to discover all the things that happen to maintain balance.