How difficult is it to say a goddamn 'Hello'?

How difficult is it to say a goddamn 'Hello'? Seriously. It's annoying at times when I get stuck after receiving a phone call. Other times (most notably with my gf, close friends) it's a breeze to utter any word. Does anyone have this kind of phone anxiety that makes it hard to recieve a call? Any useful tips to manage it?