How To Act More Mature As A Teenager. Please, be as honest as you can be; The differences in the level of physical development among sexes are more apparent around age 16. Delayed gratification — the ability to. If you were anything like me as a kid, you probably couldn't wait to grow up and be an adult. Show your bravery by seizing new opportunities as if you already knew the outcome would be awesome. Realizing how much you don't know. Not taking everything personally, getting easily offended, or feeling the need to defend, prove, or make excuses for yourself.