As-salamu alaykum brothers and sisters. I have a question. A few years ago, I swore on the Quran ...

As-salamu alaykum brothers and sisters. I have a question. A few years ago, I swore on the Quran and promised my mother that I would not smoke until I graduate from University. I am now officially a Highschool graduate and going to travel over seas. I have moved before in the past and i know the struggles of trying to adapt which let me fall into the path of smoking. Yes I know it is unhealthy but I am substituting the cigarettes for caffeine which is very unhealthy for me. How can I take that promise back as I am now legal to smoke. Do I get permission from my mother or do I wait another 8 years?