1HBHs require more time to set up than a 2HBH does. If you're trying to hit a ball with a lot of pace on the run, you're better off slicing it. I suggest practicing with a wall or a ball machine so that you have plenty of time to set up.
Setting up the shot is key. You need to put your right foot forward, turn your whole body, use your left arm to pull the racquet back nice and far, and then let it rip, but don't turn your whole body to look at the ball until after you've finished contacting it.
A lot of beginner players turn their whole body and watch the ball travel to the other side of the court. Opening up your body like that will launch the ball into the stratosphere.