If your hands are tired, crampy, sore, or moving too slowly, odds are that they're working too hard! I'll explain. When I was fifteen my French teacher unknowingly gave me a lifelong practice “assistant” when she volunteered to give Iyengar-style yoga classes once a week after school. I was instantly hooked.
A lot of teachers will try to keep your business by giving you quick fixes or showing you songs and riffs before they show you how to hold the instrument so you can actually play. Many students come to me after they “hit a wall” – they feel like they aren't getting better, their hands or wrists hurt, their technique has stopped improving, or they don't know how to find their way around the fingerboard.