If I were a school student today I would advise myself to worry less. In my school days I used to worry too much over various matters and now, based on my practical experience, I have realised that everything will not always go according to my plan but if I work hard with full sincerity then I will be able to achieve all my goals.
I would also advise myself to participate in more extracurricular activities. In school I was always trying to do better in my studies and neglected my extracurricular activities a bit. Now I think that I should have given activities like painting and swimming more time since I was good in those.
Based on my practical experience I have realised that sometimes I am not able to achieve my goals not because I am inefficient but because I don’t believe in myself enough. So I would want my school-self to believe in myself more because by doing so I can achieve all my goals.