There is a reason for your nervous tension.
After you find out what is the reason,your nervous tension will just go away.
So instead of hiding or fighting with this nervous tension, you may try to look behind it.
The reason could be that you are being too hard on yourself, worrying the listener will be impatient(actually it's you who don't have enough patience),or you would blame yourself when you couldn't do good enough etc.
The secret is to love yourself more, slow down your breath and tell yourself to take your time, no need to rush.
When you are relaxing, you can let what's in your mind naturally flow out, that's a wonderful feeling.
One more suggested skill is not to think in Chinese and translate into English when you are conversing with others. It takes longer time.
Practise thinking in English in your head in your free time, that helps!