I would suggest speaking in "softer" tones, as well as trying to smile when you talk.

The second technique is recommended for trying to convey emotion while singing, so I would guess it would have the same effect when you're speaking.

Also, I definitely agree with the body language aspect. Try to relax your shoulders and carry yourself well - in a relaxed but not closed-off way.

In short: smile more, speak more softly (at times), and relax your body language.

Let us know how these tips work out!