Remember one thing in life marks are not the only thing that will be bring the succes. Of course they are important. But more important that is the knowledge and dedication to do things( as you have mentioned that you are lazy but you try hard for improvement. Maybe you should try harder).
Marks can get you your first job but after that person’s talent and his performance decides where he will end up in life. You mentioned that you got placed(congratulation for that) even you were not among the toppers. That means you something special that they don’t have.
Give yourself time and find out all the positive stuff you have and all tge negative stuff and you will overcome those. And remember one thing as you told ki take part in lot stuff and enjoy that. Keep habbit of enjoying all this stuff. If suppose you were just studying studying like all toppers do where would have enjoyed. So don’t be sad be optimistic.
Finally marks ki piche mat baagho knowledge bataro aur marks jhakmarke tumhe milenge.
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Be happy live happy and best of luck ahead in you life.