Fear of causing unwarranted pain to another - hesitation in reaching out, betraying, perhaps, too tender a concern.  Maybe a fear that the reaching out may lead to rejection.

Yet, if that heart has already been touched, what real basis can there be to tremble, @Michelle?  The power of fear is always greatest in anticipation, I think. 

 @7f80d53a fear is often an adept liar, and can make a simple act like reaching out seem impossible.