The difficulty with halting addictive behaviour is the reinforcement brought by the immediate "positive" consequence resulted from it, which outweighs the effects of any long-term negative consequence. So, bringing forth that quitting smoking yields positive effects as rapidly as after only 20 minutes, 8 hours and 1 day is a very smart way of campaigning against this detrimental habit! :)

All the best to you @debo-medstudent,
Abigail