I am such a planner, and I'm not talking about the events type. I'm the kind of person who plans to make a plan, don't judge. I like to write down every single detail of a plan, step by step, from start to finish. This is generally a good attribute to have, if you ask me. It comes in very handy in my career.
But there will be times in life where the whole plan will be kind of fuzzy, and all you may be able to see is the first step or at most the first few steps. It'll easy to let the fear of the unknown keep you stuck at that starting point. And to allow yourself to stay there thinking you will be able to figure out the whole plan before you start.
Chances are it still won't be clear to you and your choices will be to either give up before ever starting, or to go ahead and take the step before you to the best of your ability and watch the plan unfold. And its usually these kinds of plans that are the most significant in one's life. So take the step you can and believe you're on the right track.