I've barely stuttered in my history presentation yesterday!

I've barely stuttered in my history presentation yesterday! - In November, I did a presentation and I stuttered every single time. Yesterday, I stuttered only once or twice, I don't remember! - I talked for 10 minutes straight which felt like 2 minutes for me! I even could look at the whole class and not get nervous. - What could have caused this? Why does my stutter sometimes happen and sometimes not? This is not the first time that this happens to me. Us stutterers are really strange.