In your title you said "**The more I prepare, the possibility I will stutter**." I think that some people can't make preparations one day before the presentation (making them nervous on the presentation), while others have no trouble at all doing last-minute preparations (as it won't affect them). I think it's more to do with how you view the concept of preparing on the last day. Wouldn't the same principle apply to people who stutter, negatively affecting stuttering on a presentation if we view 'last-minute preparations' differently?