Adulthood can certainly come with its share of challenges and responsibilities, but it's important to remember that it's not necessarily a depressing life for everyone. The experiences and perceptions of adulthood can vary widely from person to person.
Many adults do take financial matters seriously because managing money and securing one's future are essential aspects of adult life. However, not all adults are serious all the time, and they still find joy, happiness, and fulfillment in various ways. People have different personalities, priorities, and ways of approaching life, so you will encounter a diverse range of adults with various attitudes and behaviors.
As for whether you will have to act very mature when you become an adult, it's worth noting that maturity is not solely defined by being serious all the time. While adulthood often requires a level of responsibility and decision-making, it doesn't mean you have to give up all aspects of fun and playfulness. Being an adult means finding a balance between meeting responsibilities and enjoying life.
It's essential to develop essential life skills and maturity as you grow older, but that doesn't mean you have to abandon your sense of humor, curiosity, or creativity. Each individual's journey to adulthood is unique, and you will likely find your own path that combines both responsibility and joy.
Remember that maturity also involves emotional intelligence, empathy, and the ability to handle challenges with resilience. As you gain life experience, you'll likely grow in these areas as well. So, while adulthood comes with responsibilities, it doesn't have to be a joyless or depressing phase of life. It's about finding what brings you happiness and fulfillment while still fulfilling your obligations and commitments.