Your brain needs stimulation, and your body needs to move to make you feel good and develop. Training can be both mental and physical, and everything that you do often get you better. The best types of exercise are fun, diverse and challenging, and they build you up physically, mentally and emotionally.
You can train your brain by thinking of new ways to think the contrary, reading an article or immerse yourself in something you're interested in, solving crosswords, ask yourself "how can the others have received the opinions and thoughts they have?" and challenge your usual thoughts, ideas and habits in other ways. The main thing is that you are curious and want to learn more about life and truth.
To train physically, it is easiest that you start with something you think is funny that makes you want to exercise frequently. To play badminton, soccer or football with friends suits some, while others prefer to go out in nature, practicing yoga, dancing or weight training. The most important thing with exercise is that you do it regularly and you will challenge you in the direction you want to develop. With the help of training you can become more sustainable, more agile, stronger, have more energy and avoid or delay many so-called natural aging symptoms.