So, what? Do it anyway.
Nothing is guaranteed to work.
Isn't the possibility of success what makes the journey worth while? Still, it's called a possibility because we can still fail.
If success is guaranteed, wouldn't that take the fun out of the journey? If success is guaranteed, would we grow as much? Would we experience the pain and the heartaches that would make us stronger?
But if we stop acting (or if we don't even start acting at all), failure is guaranteed.
Things will not always work out. There's no guarantee that they will. What worked for me may not work for you.
That's okay. Try it anyway. Move forward despite the fear and the (real) possibility of failure.
Besides, courage is not the absence of fear. It's moving forward and taking action despite the fear. There's no courage if there's no fear.