To cut back is one thing, but to quit altogether, a lifetime habit, is rare to happen merely by decision, unless one is blessed with an ironclad will. Giving up completely requires a catastrophic change in ones' life, brought on by a complete change in health, psychological outlook or spiritual awakening.
One realizes that their survival is no longer predicated on and is actually deterred by the engagement of the habit that once owned him/her.
It could be celebrated as the greatest awakening in one's life, as he/she is free to enjoy a much expanded experience of life. Because, prior to his/her release from attachment to this vice, one's awareness was stifled and relegated to the limited physical pleasures of sensation derived by interaction with another mass of flesh.
The amount of time and money consumed by this habit could be immense, and in a sudden shift of consciousness, one could realize that it just isn't worth it anymore and it is not worthy of consuming ones' entire life.
I have a friend approaching 60, spent his life mongering, married many times and recently just lost his zest for sex. I mean, a remnant is still stere and he could pop a blue pill but he feels that the blue pill has an artificial unnatural foreign quality to it that he despises. I offered him the herbal approach but he was very frank with me. He told me that he was yanked around in every possible direction his entire life by his addictions. (he also was a drinker in his past) And, now that the sexual addiction has left him, he feels a greater enjoyment of life, to just be by himself and think freely and engage in life without the sexual urge coloring every action.
I just listened to him with an open understanding heart and got what he was saying. Realizing that I am not quite at that point.