The greatest performances always allow for imperfect or awkward speech. Phrasing drop-outs, hiccups, stumbles, running out of breath, etc.
Prime example #1: Marlon Brando delivering Marc Antony‘s “friends, Romans, countrymen” speech in Joseph L. Mankiewicz‘s Julius Caesar (’53). At 2:08 Antony, overcome with emotion, says “bear with me” to the crowd, and then “my heart is in the coffin there with Caesar, and I must puh…pause ’till it comes back to me.” Brando stuttering on “pause” is deliberate, of course, but it sounds and feels right.
Prime example #2: James Caan‘s Sonny beating up Gianni Russo‘s Carlo in The Godfather (’72). At 2:52, after kicking Carlo a few times in the ribs, Sonny says, “If you touch (beat, catching his breath) my sister again, I’ll kill ya.” I’m presuming this wasn’t planned…Caan was tired from the exertion and just ran out of wind, and director Francis Coppola liked the realism.