Fear of failure, fear of success, lack of clarity, self-doubt, perfectionism, external pressure, staying in comfort zone, overwhelm - goal is too big, lack of resources, procrastination, endless planning and preparation, distractions, pleasures, lack of belief in possibility, no urgency, no support, fear of loosing control, feeling alone, being ridiculed.... the list is endless.
To break the barriers, the first step is action. It can be small and imperfect. Eventually it can create momentum.