We can often tell what words we will be disfluent on. That is not a mess up though, you didn't do anything wrong, you stuttered. Interesting side note, we often over estimate what words we will actually stutter. When we think we will stutter our tension increases and we are more likely to stutter on those words. In other words, we may be right only 50% of the time but our fear of stuttering increases our tension guaranteeing that we are right 100% of the time. It's better just to talk without scanning ahead and let the stutters fall where they may, many people will find that they stutter less this way.