The short answer is that you never know for certain. For example, people used to believe that Newton's law of gravity was correct. Now we know that it's not as correct as Einstein's theory of gravity. And it's easy to see that Einstein's theory is not entirely correct either, because it fails to describe the rotational motion of galaxies. Until you discover a reason why your theory doesn't work, you can use it.
There are certain "traits" of a good theory though. For example, a good theory gives new results, it doesn't just describe things that already exist. It's like a gift that keeps on giving. Another trait of a good theory is that it's economical. It does not rely on unnecessary concepts.
There are some theories that you just know they are wrong, they call them phenomenological theories. They are basically a hack to describe a phenomenon until a better theory comes along, and this is known at the outset. A phenomenological theory is like a band-aid. For example Plank's description of black body radiation was like that. There was no underlying reason why it should work the way it did, and it bolted on to the current theory the idea that for some reason radiation has to be quantized. Today we know why radiation is quantized and when it's not. Radiation is quantized when it's constrained in a limited space, like an atom, a cavity, or an optical fiber. We don't have to bolt that on, it just "falls out."
Another good trait of a theory is that unifies, it simplifies, your current knowledge, it does not add new primitive concepts.
To me the idea that the failure to do what is in my best interest is the result of a faulty das is the most economical way I can describe my problems. This is a promising trait. The results of relying on this theory are very good, also, and they are tested by thousands of people every day. Mindfulness consistently gives good results in people's lives, when they use it. It's true for engineering, manufacturing, stock trading, yiddishkeit, and increasingly also mental health. I have also tried other popular methods of recovery, and I find mindfulness to be the most decisive and rapid.
And when I learn Torah I don't need to justify why it's okay to use my recovery method, it's already in the Torah. We are told that if we are mindful we can change. The question is: how come it doesn't work? My current approach gives an answer, and the answer enables me to stay clean, be nice to my wife, enjoy my kids, and grow in Torah and mitzvos as well.
If you are interested in this from a scientific standpoint I would watch "the character of physical law part 7".