I assume it is with you like many of us, that it isn't nearly as bad speaking face-to-face with someone than say over the phone. A trick I usually do when that one word simply refuse to cooperate is to stop, smile at the person(s) listening, smile and say "sorry" (with a grin). I've found that to be a sort of ice-breaker. It loosens the tension for me (the speaker) and the persons listening who are not sure how to react because they see you are struggling. Somehow you then acknowledge that you are struggling, and by smiling and "laughing it off" you also make the people around you a bit more comfortable. Which in turn makes it easier for you to speak. This *of course* varies from person to person, but it works for me.