Part of why smokers have difficulty quitting is that they are also erasing a familiar identity - that of a smoker.  They are saying goodbye to a cluster of habits, associations, and memories that are a part of them.

You become identities - a parent, an employee, a bicycle rider.  But why not choose these identities?  As with so much else, you can choose and change your identities, and start to build new clusters of habits and associations around the new identities that more closely match the person you will become.