Fighting martial arts are effective. Practice makes perfect, or at least pushes you closer to your goal. Forgive my tiresome use of analogy for a moment, but no one will argue that lifting weights makes one stronger. Yet, I'm sure you know many people who have experimented with weight lifting without showing significant gains in size or strength. It is the same with the martial arts.
Consistent training is necessary for results.
If you stop training, your abilities will fade. Maybe that black belt meant something when you got it, but if you haven't been training for a while, you may not be worth that piece of cloth around your waist. It's all the frills of the martial arts that throws off the effectiveness of the training. These are the easiest aspects of training and, unfortunately, the least combat oriented. People get caught up in belts, forms, fancy outfits, sifu this, and sensei that, because they are the easiest to practice.