Growing up and reaching adulthood is a natural process. As people age, they develop different qualities, and their behavior and mindset improve. The phrase "become mature" is commonly used to describe this process. However, there are numerous synonyms for this expression. The phrase "achieve maturity" implies that someone has reached a certain level of growth and understanding. Another synonym is "ripen," which refers to the process of fruit becoming ready for harvest. "Develop" suggests a gradual change or progression towards a more mature state. "Cultivate" is also a useful synonym, as it suggests the intentional effort put forth to grow and mature.