It depends on your tolerance to the amount. There’s a classic lesson in the film “Mean Streets” where (I don’t recall the characters or actors) the younger “apprentice” is owed $20 by one of his counterparts. He wants to take some kind of action, but is advised by his “mentor” of sorts (these people are all criminals) to view it as a small amount to lose to learn that his counterpart is a loser and bad partner material.
On the other hand, I personally found satisfaction by being aggressive in collecting a larger debt that was once owed to me by a friend who asked if she could rent from me as part of a move back to my town. She ended up owing me around $1,100 and more or less snuck out the back door without leaving a forwarding address. After unsuccessfully trying to locate her (she was still in town) for a few months, I found her mother’s address online and knowing that her mother knew how to push her buttons wrote her mother a six page letter detailing all the things I had done for her daughter over the years and the debt she owed with a request that the mother buy out the debt.
I was paid in full a month later and not without “how could you do this to me!” kind of commentary. I rationalized that her actions forced me to be a dick, so I did not feel bad about being a dick. I got my money, which was helpful because that wasn’t (and still isn’t) an insignificant amount for my budget, but more than that I didn’t have to do the whole emotional process of getting over being sucker punched.
I would say there’s a third path if you are truly an enlightened sort of being and that is to recognize and identify with your “higher Self” (for lack of a better term)—your Self that comes before your consciousness. That higher Self is not diminished by unreturned money or by your friend’s folly.
I helped someone else on Fluther recover more than $10,000 from a working attorney(!) friend who was being a douchebag by advising her to resort to shaming him (although she did it by sort of threatening to make the debt publicly known among his attorney peers through legal action) much like I shamed my friend. It’s a useful lever.