One of the relaxation techniques included in Stress Free is self-hypnosis. Dr Freeman will give you a step-by-step simple guide to achieving a state of hypnosis without having to go to see Derren Brown. Not everybody is able to achieve this state, it depends on how suggestible you might be. I know it sounds woo-woo but there's actual science here. For instance there are scales that measure how susceptible to hypnosis you might be. The most famous of these are the Stanford Hypnotic Susceptibility Scales, one of which you can download here if you are curious.
A recent review in Expert Review of Neurotherapeutics asserts that "self-hypnosis training represents a rapid, cost-effective, nonaddictive and safe alternative to medication for the treatment of anxiety-related conditions" which is why we like it.
So you can stop worrying now, as you can see it is safe and side-effect free. There is no chance of you becoming a barking dog or a clucking chicken... unless you enjoy that sort of thing.