I think this is pretty common...the closer your mind comes to making that decision to fully commit to stepping over the edge.
However, you shouldn't think of it as "taking the plunge" into a bottomless pit from which there is no turning back, because that would terrify anybody and make them constantly second guess themselves. Instead, I think you should approach it as something like moving out of your parent's house for the first time...you are leaving everything you have known, everything comfortable, most (if not all) of your friends and family. You are heading into the unknown, excited and anxious and probably more than a little bit scared. But you need to remember you are not the first person to do it, and most of those who have done it are faring pretty well right now. There is support and help available along the way. Your new home might not be perfect, especially in the beginning, but you will learn the neighborhood and grow with it.
Ultimately, if it doesn't go as planned or you find out it isn't for you, you can always move back to your original home. It won't be quite the same as you left it, because you will no longer be the same person. But it will still be your home, and you will be stronger for the experience of leaving and will better know yourself.
I understand it is not nearly as easy as my analogy, and I am currently struggling with some decisions myself...not so much about if I am transgender or not, but what I should do next. However, for many people I think a lot of fear and apprehension stems from thinking of this as a be all/end all decision and a one-way journey...once you make the choice, nothing will ever be the same and you can never go back. However, you will always be you, and nothing but death and taxes are immutable.
