The usual side effects of quitting smoking without the help of hypnosis are very unpleasant withdrawal symptoms which start after around 2 hours and continue for about a month in many cases and sometimes longer.
What happens is that when you started smoking you convinced your unconscious mind that keeping you smoking kept you safe in some way – often from being laughed at by teenage peers or some similar situation.
The unconscious mind is like a 3-5 year old – very single minded and relentless about doing what it has been told is right and maintaining the established habit. To quit smoking you need to change your unconscious mind.
If you fail to change your unconscious mind, it will behave like a child throwing a tantrum (I am sure you have all witnessed this in a supermarket even if not in your own family). Cravings and withdrawal symptoms are simply an unconscious tantrum and this can be prevented using hypnosis.
But did you know that nicotine is not addictive for more than around 2 hours. The addiction is to the habit which has built very strong neural connections to reinforce the habit. These get broken in hypnosis when the brain is flooded by serotonin as a result of the very deep relaxation and the guided visualisations.