The best thing I did to help me with thoughts of failure was planning things out to a really good outcome, then defining goals that were very easy to attain, and solicit advice from these easy goals from people I know are going to be supportive.
It has taken me quite some time of these easily attainable goals to build my confidence up, but now I really do get the feeling I can do this. I am going to keep building my confidence and eventually I will get to a point where I cannot be brought down by external situations. This is why I decided it was going to take me 18 months of hormones before I could consider going full time (even if boobs are really getting in the way of my time frame) because I really want to build up confidence in every possible way before I take the plunge so to speak.
For a while, I had some doubts about being fake, mainly because my dysphoric feelings came in waves, and between those waves I thought, maybe I could handle it. I realized though, really what was going on is I was trying desperately to make some sort of excuse to save me from all of the hard work, heartache, and change that goes along with transition. I thought about it like this, if it was as simple as snapping my fingers and being a girl, would I do it? Of course I would, so it isn't the gender that caused me concern it is transition itself, and and difficulty is kinda irrelevant since life itself is difficult. I am being authentic to myself by transitioning.