The 90/10 principle states that 10% of life is made up of external events outside of our control, while 90% is determined by our internal reactions to what happens. How we react to situations, both positive and negative, has a significant impact on our experiences and outcomes. While we cannot control what happens, we can control how we respond. Maintaining a calm, rational reaction can prevent external factors from ruining our day and minimize stress. Understanding and applying this principle can change one's life by gaining more control over our experiences through managing our responses.