Indeed you don't have to be religious to change. I, too, was once a heavy smoking, heavy drinking, swearing, womaniser. God had nothing to do with my changing - it was my own realisation that I was letting people down, pissing them off and playing fast and loose with my health. Selfish reasons, if you like! And I, too, prefer the 'new' me to the old (even if some say I've become boring) - but I can have the pride in a job well done rather than letting a god take the credit! ;-)