There are two different questions that often get mixed up: "What can hypnosis do in general?" and "What can hypnosis do for me?"
In general, quite a lot is possible — some people can be hypnotised deeply enough to sit in a tub full of ice without feeling the cold. That shows what humans are capable of, the same way it's true that humans can run 100 metres in under 10 seconds. Both statements are true, but only for a handful of individuals at that level.
For you personally, that means: most people can draw noticeably more out of themselves and get closer to their own potential with hypnosis, without ever needing to reach those extremes.