Sit on your bike in your normal riding position, lean forward and rest your palms on your grips with your fingers outstretched straight in front. Your fingers should rest on your levers and imagine a straight line drawn through the length of your arm and outstretched fingers. This is the right position.
Your body position when braking hard is way different to your default body position - positioning your brakes for this makes them much closer to horizontal. Also, dropping your wrists will give your hands a much more secure position on the bars and you need higher levers for this to be comfortable. Just measured my brakes and the levers are 15 degrees below the horizontal when I'm not on the bike, so 15-20 deg when riding.