No. Hypnosis is a streamlined state of focused attention, much like being absorbed in a book, a film, a sport or a creative activity.  You have the ability to emerge from hypnosis at any time if you wish. Think of me as your guide; I am the facilitator, but any change comes from within you.  Recognizing your control and ability to initiate change can be incredibly empowering.
The more often you choose to go into hypnosis, the more comfortable you become with the process, knowing that you are always in control and can choose to end the session whenever you desire.   As most people find hypnosis deeply relaxing and a very pleasant experience, they rarely choose to do this, however, it is important to understand that the option to do so is always available if you decide it is necessary.