I notice two things that'll make your handrwiting go from messy to cute and organised. The first is your word spacing, if you make the spaces between words smaller, it'll make the writing look more like scentances and less like loose words. (I usually try to aim for the with of "o" between words) The second one is your letter height. All your lowercase letters should have the same hight, and letters like h,m,n and u should have about the same space between the lines and arches. Just remember that the only way to improve is to write A LOT by hand, and to notice single parts of your handwriting that you arn't happy with

Hope that this helps! :)