Music singing question?

So This morning, and every other morning I woke up and was able to do this REALLY high stream of notes. Like I'm talking Mariah Carey High. Or to put in better words I've been doing whistle register. I had no strain to my voice or anything, and the question is, is it good that I can use it? Because I was told you can either use it or you can't. And you can't really learn to use it.... So what is your opinion on this?? thanks ;)