How do you speak when you are too nervous to do so?

It's a vicious cycle. In new situations, where I must speak, I get really nervous, and have trouble talking at all. I'm afraid that when I do speak it will sound angry, unhappy, or just plain weird to people around me, and that will make them uncomfortable. This worry makes me even more nervous. How do I stop it? Relaxation only goes so far. Using certain thoughts to put myself into a trance can work, but it takes diligence. Any suggestions?