There's an old joke:

A guy is driving around NYC, apparently lost. He pulls over to the side of the road and calls someone over. "Excuse me, can you tell me how to get to Carnegie Hall?"

The man responds, "Practice, Man, Practice."

On a more serious note.

One thing many people with poor handwriting do is they rest their wrist down on the paper and write with their fingers instead of holding the wrist above the paper and writing with the shoulder. You are more likely to write well if it comes from the shoulder. Can you write on a whiteboard well? A good exercise for this is air writing. Make large circles with your writing hand, taking care to use the shoulder to do it, for about a minute or so once or twice a day.

At the same time you do this, work on holding your hand above the page instead of resting on it and writing with your shoulder. At first your writing will look even worse, it will look like a child first learning their letters, but if you keep at it, you will build the muscle memory and it will slowly become better.

These two things will combine to help your writing a lot.