I have no idea about hypnotizing yourself to get physiological results (e.g. women getting 'hypnotized' to grow bigger breasts), but in my line of work (i'm a motivational speaker/dating coach), hypnosis is pretty common. What i've found is that it's good for short term results but anything long term needs to be as a result of a change in behavior or thinking.
For example, if you're experiencing a lock up when you want to approach a beautiful woman, i can give you a neuro linguistic programming exercise that will temporarily alleviate the anxiety...but it's only only a cure for the symptom. Ultimately you'll have to just approach constantly to get over that fear. I don't think it ever really goes away entirely (just like the fight or flight response when you get into a fight), but repetition sure makes it easier to deal with.
Guys have been trying to hypnotize themselves to be confident for years now, but they're only deluding themselves. The first time they get rejected, their house of cards collapses. You have to develop confidence by DOING stuff. You can't sit in your room all year and try to manufacture it out of nothing.