Morality V.S. Inevitable Violence?

I have a degree. I study a lot and I also know a lot right things from wrong things. But in real life, especially in loan-interest business, when someone don't pay me, I always want to beat or curse them although I don't want at all. sometimes I fight with a person who owe me money. what should I do? If I don't fight and curse those cheating guys, am I crazy to give them my hard-earned money for free without interest? Of course I also think of interventions from police or local authorities, but they are just slow and usually ineffective. I mean I don't get both my money and interest rate. What would you do if you were in my shoes? give those sons of a *** some lesson or what?