Who wants to know?

We aren't scared of the dark, we're scared of what's in it. 
We aren't scared of heights, we're scared to fall. 
We aren't scared of love, we're scared of rejection. 
We aren't scared of water, we're scared of drowning. 
We aren't scared of trying, we're scared of failing.

So if we think we're scared of one thing but we're really scared of something else, what are we really scared of??