Play more.
Try different hand positions and grips for your mouse/pen hand.
Always play a little bit above your comfort level.
Play more.
It always comes down to practice. The more comfortable you are with your mouse, sensitivity, and grip, the more consistent you will become. Also try to play for fun and not go for good scores all the time, or you will get disappointed by your plays and play worse. I personally have nights where I'll just play some unranked or songs that I'm not good enough to get a score on, and nights where I spam ranked maps. It's good to change things up.
But honestly just play more, look at the performance gauge at the bottom of the screen and take note if you are hitting too late or too early, and adjust accordingly.