Calling End-Users

So I've been working as a Tier 2 Infrastructure support analyst for about 4 months now. My previous and only job before that was an internal Sys Admin role for a company of about 80 that I worked at for just over a year. I love this job as it's been a whole lot less stressful, and I get to work at home which is a bonus since the commute is about 45 minutes from my home even with good traffic. The part I struggle with is calling end-users. Since I do support for infrastructure which is in the realm of network devices and servers, I can sometimes go days without having to make a call to a user. But for some reason, the idea of calling someone and not really knowing their attitude, or temperament, or mannerisms really bothers me and makes me anxious going into the call.

For the more experienced of you in the Service Desk, how do you deal with this anxiousness of potentially calling someone who isn't very friendly? Or aggravated beyond friendliness?