I believe writer's block stems from two or three causes. The most frequent reason I get stuck is that I'm unprepared to write an upcoming scene or portion of my book. I haven't done my research or I haven't planned the material well enough. Another cause for writer's block can be that I've made an error somewhere. Perhaps my protagonist's motivation is implausible or I've allowed the villain to ease up so the conflict is dwindling. My story sense is good about nagging at me to stop, re-evaluate, and pay attention to what I'm doing. And sometimes I think people become blocked for some emotional or psychological reason. They're afraid to try or they're afraid they'll offend someone in their family. Maybe they're afraid of making mistakes and being laughed at. Usually they're hindered by a very potent inner critic. My answer is to face whatever is inhibiting you and take a chance. Your story doesn't have to be perfect and you shouldn't expect it to be. Just write and keep writing until you become better.