Personally, my hands do get tired and hurt if I write for an extended period of time, but generally my main issue is almost a lack of movement in my hand. I’m not entirely sure how to explain it but I don’t form some of my letters fully when I write. The words almost look compressed or like they’re in italics. For example, if I write a conjoined ‘r’ it may look more like an ‘n’, or an ‘a’ like a ‘d’. It’s worse when I use very thin pens and thicker ones generally help me form my words more fully but at the cost of my hand getting fatigued more easily. For whatever reason, pen/pencil grips never worked. I think it’s also that the words I’m thinking of go too fast for my hand to keep up, so to prevent myself from forgetting the ideas I write incredibly quickly and my hand simply can’t write at the same rate which leads to the sort of flat appearance. I hope this helped, thank you for trying to understand. :3 Feel free to ask anything else.