How can I reset my nerves?

As a result of having a very stressful job, my muscles - specifically the muscles in my gut and lower back - are tense all of the time. It's been like this for a few years. Somewhere along the way my nerves began to compensate for all of the tension and began to produce excess saliva into my throat and mouth. But now even when I'm not in a tense situation I've still got drainage in my throat and my mouth is watering - so I've got to swallow constantly and it's very bothersome. What can I do to reset my nerves to calm them down and eliminate all of this drainage? I just want to be able to speak easily again.