a fear of quitting

My job hasn't made me happy for a long time now. The people are great and I can do the job in my sleep but I've needed a new challenge for years at this point and this is where my issue lies. I'm at a loss on what to do next, to the point that I've been frozen in fear of moving forward. It sounds silly, especially with how simple the 'experts' make it sound, although simple doesn't always mean easy I guess. I'm aware that it's all down to fear. Fear of change, fear of failure, fear of making a mistake. I'm so comfortable where I am that I can't seem to find the motivation or discipline to do anything about it. I keep thinking if I hand my notice in, perhaps that will give me the crunch I need to make a move, but then the fear of failing creeps up and I'm back to square one. It is simple to 'take that first step' and make the change, but it's definitely not easy and it's giving me sleepless nights over it. I have the spark of an idea of what I could do next, which is to go into…