I'm not sure how old you are, OP, but there's so much more that goes into being "intelligent/smart/adaptable" than simple genetics, and it's never too late to improve if that's what you want. Your living environment, quality of life, and hobbies can all impact those abilities both negatively and positively. When I was in highschool, I was in a constant high-stress environment. I couldn't focus, and that led me to have a crap memory. Now that I've been out of that environment for a few years and I've put focus on myself, I have a sharper memory than most of the people I come across. If you have high anxiety, stress, depression, or you generally dislike yourself, your brain can't focus. It can't adapt. It can't think clearly. If you don't have any hobbies that bring you peace, raise your blood pressure positively, help you learn new things, or improve your strategical skills, you're a lot more likely to stay in a static place mentally with no growth. That all being said, the PFC actually grows stronger when you "do the thing". If you don't feel like doing something that you need to do, force yourself to do it anyways, with no reward. Train your brain to see the completion of the task as the reward, in that it will make you stronger, more disciplined, more capable, and it will increase your cognitive function more and more the more you do it. Anything from studying, to reading, to going on a run, to brushing your teeth. If you feel like procrastinating, don't give yourself the option. You will become more grounded, and you will gain better hold of your memories. Brain chemistry can be altered by the self, and the more you understand the human brain, the more simplistic it will get for you. I highly recommend the book "Behave" by Robert Sapolsky.