Improving your handwriting is pretty simple, it's just mildly time consuming. I journaled for a month and just focused on how I wrote each letter. At first it took me half an hour to fill an A5 page - but my handwriting looked so good! It only took a month for my muscle memory to pick up the adjustments, and now I can write quickly and legibly in cursive.

I tell everyone who mentions bad handwriting the same thing. Buy a cheap journal, grab a pen you like, throw on something to listen to (music, a podcast, the news, a game stream, could be anything) and just write. What you write doesn't matter, just focus on putting down each letter exactly as you want it to look, and take your time.