>>270092864
Depends on your controllers and what you're currently struggling with. If you're not able to read the upcoming notes and know where you need to swing next, then the only remedy is more practice. Try playing more maps that are well above what you can do in no fail mode. This will help you learn the common patterns present in higher level maps. 
Aside from that if you know where to go but just can't get there in time then the biggest tip to move on from hard is to start using more in the lower arm. Use the biceps, wrists more than shoulders etc. Experiment with different grips on your controller to bring the center of mass closer to your wrist if necessary.
You want to position your arm to flow with the blocks so you can move faster. You need to snap through the blocks essentially. Think of it like throwing a virtual baseball, your arm can give you power and direction but the flick at the end is where most of the speed comes from.