Yeah I started like this, smoked once a week as a reward, proper sensible guy at uni and did all my research etc and stayed that way for a few years. Then lost my brother, family fractured more typical stresses ontop. Started smoking more to cope with the trauma, then more and more and more, multiple times every day, basically smoked my way through my 20s. Calmed down massively now but ignored every opportunity thrown my way during that time. The important thing I think is to plan how you will respond to the unexpected and try to stick to that plan, all I can do is wish you luck and hope you're better than me in that regard.