I get this question a lot: “How do I improve my handwriting?” There are books and sites that go into this in detail. I’m not an expert, so consider this the equivalent of an eyewitness anecdote rather than anything scientific.
The brain loves patterns and symmetry is one of its favorites. We find consistency pleasing in many things, including handwriting. A scribble can be beautiful if the spaces between letters are even, or if the heights of the small letters are the same.
Consistency in angle, letter size and spacing will make your current handwriting look better and more pleasing. You don’t have to overhaul your penmanship; you can start from your current style and increase its consistency.
Quadrille paper is your friend when it comes to practicing. Make a box and fill it with an a or a c. Repeat many, many times. Draw boxes around your letters and check if the boxes are more or less the same size. The box is also an angle guide.
Quadrille paper is also useful for practicing descenders and ascenders of the same length and height. Write consecutive letter g’s and make sure the lower loops look the same.
The slant of your handwriting is up to you. What’s important is it’s the same all throughout.
Practice a lot. Write the same letter over and over again. You won’t have a social life but hey, you can always write your friends a really lovely letter. Start with the letter a.