going in and out of the habit is quite dangerous .. that's how the lung cells got confused... usually they are long cells (called epithelial cells) then turns to a much stronger type of cells, the squamous cells (like the cells found in our skin)..
if you stop then goes back again with the habit, these cells are constantly changing from stronger to normal type then vice versa.. causing metaplasia --then cause cancer cells..
I'm happy you're doing great with the program!. More power and keep it up!