Singing doesn't have to be hard, scary, or overly complicated. There is SO MUCH you can do with zero guesswork to improve, especially when it comes to hitting those high notes. This is going to sound STUPID simple, but I'm tellin' ya, it works. If you're trying to hit a high note and struggling, ask yourself, am I giving it all my volume? If not, sing it LOUDER. That's it. It is WAY easier to sing a high note loudly than softly.