The first option is practice. Each hit of the wood by hand strengthen the hand and you get used to the pain. The same here: to overcome a fear — get closer to the source of fear. A good tutor sitting next to you, who explains every tiny detail, helps a lot. Keeping in mind the fact that the monitor is a sort of barrier and, actually, there is nothing to be afraid of, also helps. When you feel comfortable, it is hard to be scared by something. As for me, to stay away from being too familiar, my tutor has explained me the importance of maintaining a distance with the customer through tickets' analysis.
We understand it this way: a customer is not a stranger to us, but not a member of our family also. Here, the practice is important, and from distancing a customer you can go to being open and kind, though not too much.
When it comes to humor, we have the rule that jokes should be as accurate as possible. In other words, each joke can be read seriously. Those who got the joke will laugh.