grace, i'm familiar with a similar exercise....only it's brushing your teeth. whatever hand you normally brush with, change to the other hand. a habit like teeth brushing is so automatic we don't really THINK about it, we just grab the brush and the toothpaste and go! especially if this is early in the morning, we are already operating on auto pilot.
it takes careful THOUGHT to change a habit. our hand reaches out, we go thru the motions, and maybe during the frothy brushing we remember, oh yeah, that's right I was going to use the other hand. and so we switch, and it's all awkward and uncomfortable.
our habits aren't just created in our minds.....our bodies respond thru motion memory. we become conditioned. and making any change to that conditioning takes time and work, lather rinse repeat.
but addictions are more than just habits. it's a mental obsession coupled with a physical compulsion....we crave/need the substance at a cellular level. our bodies have adapted so that the substance becomes a necessary part of the equation to feel "normal" - even tho our normal is skewed. that's why we go into withdrawals if the substance is withheld. and why we have cravings....in those moments all the addict knows is that MORE will make the insanity stop. (former crack addict here).
the desire to quit has to come from a very deep place, you could call it as being at the level of the soul. talk won't cut it. pleading, tears, threats rarely can reach to that dark place. you might as well say, well just stop breathing. i'm not trying to give the addict an out....it ain't the quitting that's hard....it's the staying quit.