Probably not nervousness, but instead you not being familiar with being put in a trance, so the trigger might not have been established well enough to control the effect. This combined with your own preconceptions and wishes for it to work the first time, is likely just making you think that its having an effect when it is really you wanting it to have an effect which is causing this.
If you want it to stop, just stop thinking about it, listen to some music, or do something else which can keep your mind occupied. If you ignore it, it'll go away eventually. If you want it to continue, try listening to the file more, maybe looping the body 2-3 times before waking up if you know how to work with files, eventually you will have the trigger working right, and can use it.