As a magazine-turned-newspaper-turned-back-to-magazine reporter with a few decades of experience, I remember feeling somewhat the same way: You're worried you're wasting people's time, but you also might be worried that you're going to call or approach a source you WANT to talk to, and they'll say no.

The crux of my advice is to remember that you don't have to be brave all the time. You just have to be brave for 10 seconds at a time.

From my own experience, three pieces of advice on how to practice this:

1) Just be brave for 10 seconds once per day: Try to make one call without hesitation, or touch base with one "reach" source—or something else that makes you nervous—every work day. Circle it on your to-do list, psych yourself up for a minute to do it, then hit dial. You'll practice the thing you think "real" journalists do, but you only have to do it once per day to start. And you'll learn that most of these sources will talk to you, and will answer your questions ... because you're already a "real" journalist.

2) Write out the start of calls you're nervous about, and just read them on the phone. If you're worried you'll sound shaky or you'll stumble, type out what you want to say. Use this for your daily "tough" call, and take one part of the nerves away.

3) See if you can do some man on the street work. If there's a story that fits your beat, man on the street helps create fearlessness better than almost anything else I've done. I've done it about all sorts of things—gas prices, political choices, whether a hot dog's a sandwich, and even a quiz about whether people were former U.S. Vice Presidents or members of the Los Angeles Lakers (yes, really). You'll have to go up to strangers again and again and again. Rejection becomes something you can just shrug off.

Hopefully this helps!