Get minimum of 10-15 minutes of sun exposure everyday.
Maintain an active life, you need not go to the gym just do some basic body movements that will stretch all your muscles and move every joint in your body.
Play sports or games with friends or family members, you can try badminton, cycling, running, carrom even PC/console games are also a great way to start, It keeps you mentally active rather than scrolling through the internet. Try to engage with real people for activities as much as possible, make new friend, find new hobbies.
Just going to a supermarket for grocery shopping instead of ordering online will make a big difference.
Routine play a very important role. Make a timetable that you can follow, be disciplined but don't stress out if you miss something, just try your best to complete it. Have fixed sleep timings, keep your phone away from your bed while your sleep.
Life is about balance make sure to include entertainment, fun activities, even your social media activity but just limit the time that you spend on it. Don't become a fitness monster it's okay to indulge in comfort food every now and then.
Purpose of life is simple to me, it is to learn, explore, teach, serve, contribute and create harmony where ever you go. Enjoy whatever you do, do it with responsibility, everything you do has a small purpose to it that you don't realize always thinking about the bigger things. Have your own opinion and make the world a tiny bit better.