I can but assume that the people who fail to get their money are victim to one or more of the following:
1. Lack of conviction - they wimp out when (or before) they get to court.
2. Confusion - they get emotional and fail to present the court with clear and dispassionate evidence.
3. An experienced fraudster - even after a court judgment against them, some people do a runner, or lie about their income, and drag out the payment until you give up chasing it.
On principle, even when faced with the probability of the third outcome, I always sue. Even if it costs me the court fee and loss of two hours earning time, I always sue. I once sued a customer for £5, which cost him £45. I've sued BT, MFI, and Dell Computers. None of them went to a hearing, and all of them paid me in full.
Don't get mad; get even. Put everything in writing, and keep a diary of every single letter, and phone call, and action that you take. You might think that you won't forget the detail, but having to remember is stressful, and you need to remove all stress in order to gain maximum credibility in court.