People sometimes wonder whether they will get ‘stuck’ in hypnosis. I'm pleased to be able to tell you it's no more possible to get stuck in a hypnotic trance than it is possible to get stuck in a dream when you are sleeping (which is a kind of naturally occurring deep trance state).
Nature needs us to be in different states of consciousness from the day dreamy state of hypnosis of work to the high-energy state of cheering on a sports team or dancing wildly at a party. We all need to change psychological and physical states often. So, people always awaken from trance although sometimes they may feel reluctant to when they are having such a wonderful inner time.
There is sometimes a kind of relaxing ‘heaviness’ in the hypnotic trance experience. What’s more, this natural heaviness, or catalepsy, also occurs during dream (Rapid Eye Movement) sleep although, because of the unconsciousness of sleep, we don’t tend to recognize dream-time physical heaviness. Nature provides us with catalepsy when we dream as a safety mechanism to stop us physically acting out our dreams. Nature tends to be pretty sensible which is why you don’t get stuck in hypnosis.
Because of the similarity of hypnosis to the dream state, catalepsy can sometimes occur spontaneously, or it can be induced by suggestion. This natural catalepsy is one of the reasons why hypnosis is so good for pain control. But central to each person is a strong survival mechanism. Even though you might be dreaming at night and deeply cataleptic if someone yells "fire” a few times you will wake up and all the heaviness will vanish. And that’s from a state of sleep.
I once induced eyelid heaviness/catalepsy in someone I was working with in a hospital. She felt like her eyelids were “stuck together with relaxation” and couldn't open them when she tried, but when the hospital fire alarm went off (although, as it turned out, there was no fire) and she opened her eyes immediately.
We need to be able to attend to outside reality in an instant if necessary. Tens of thousands of years ago our ancestors may have “tranced” out around the cave fire but if they heard a predator outside they had evolved to snap their attention back to external reality.
Where was I... oh yes, so that's the long answer, and the short one is, no, you can't get stuck in hypnosis because of the innate survival value of being able to come to full waking consciousness instantly should you need to.
And I'll end with the comment that hypnosis should always be provided with the intention of giving the person hypnotised more control in their life, not less.