It's not at all difficult
if you have been damaged. Libel and slander are two obvious ways in which speech can be damaging (all right, libel is technically not "speech," for those of you keeping score at home), but there are many others.
- breach of contract -- you agreed not to say something and you said somehing
- copyright violation -- I have property rights in whatever you said
- trade secrecy -- this, of course, is a combination of the above two; I have property rights in the idea you expressed, and you agreed not to reveal them
- tortuous interference -- you induced someone to do something to my disadvantage without just cause.
- breach of privacy -- you said something you aren't legally allowed to say (for example, revealed my medical history improperly)
- fraud -- you told me something that wasn't true and got money from me as a result.
- malpractice -- by speaking, you so greatly violated professional norms that I got seriously hurt
- et cetera, et cetera,...
The key as I pointed out, is
damage. Show me the money. Your hurt feelings and $1 will get you coffee. On the other hand, your hurt feelings and a demonstrable financial loss of $200,000 will probabably get you at least $200,000 plus costs and fees. (AND coffee, if you want it.)