Motivation is a problem no matter whether you smoke or not. Retaining interest in things over a lifetime is a problem whether you smoke or not. Smoking just makes you feel good (Sativa) and the day passes more gently. In the end you are who you are. Stories of potheads who quit and went on to do great things are matched by stories of potheads who do great things and plenty of people who don’t smoke weed who do nothing of worth in life. So pot is just a lifestyle choice not a determinant of who you are and what you do with your life.