In trying to understand our minds, we find this phenomenon where the mind obsessively repeats a destructive thought, magnifying and distorting it way past the point of normalcy, until that thought completely occupies the mind and overwhelms one with its intensity. Why does our mind work this way? Is there a constructive reason that Hashem programmed us like this? What is the effective way of dealing with these types of thoughts?
With Hashem's help, I have come to understand that these types of thoughts are analogous to a child who is distressed by a certain illogical fear or deep feeling. As they are told that their feeling has no rational basis, and the emotion is quashed instead of first being acknowledged, the pitch and frenzy of their illogical assertion rises in frequency. The intensity of their insistent repetition comes not from a belief of their correctness, but rather, from a deep need for the helplessness of their emotional state to be recognized and acknowledged. The louder and more intense the cry, the greater the need for reassurance before a voice of reason can be heard.
Similarly, when the mind encounters a situation it finds emotionally disturbing - a situation that seems out of control - the pitch and frenzy of its need for acknowledgment rises, to the point where, if not properly addressed, it completely occupies the mind with its distorted emotional view. The underlying subconscious intent is no different than a child who is screaming something illogical, but is really saying, "Acknowledge my feelings." We need to acknowledge our own feelings and release the tension and helplessness that is at the root of it.
This ideas starts to release its true power when we understand that one of the most fundamental needs of a human being is that he feel that his situation is under control. One of the most difficult sensations a human being can face is a sense of helplessness. The human being will do anything in his power to escape this feeling. The healthy person will begin taking action to ameliorate his situation. The emotionally unhealthy person will use any number of unhealthy means to escape into a fantasy world where the lack of control is no longer in the forefront of his mind. This feeling is what causes the mind to scream the distorted and magnified helpless thoughts to the point of obsession. It is rooted in a childlike thought process that says, "If I scream louder and make it sound worse, perhaps then my intellect and conscious mind will take this issue seriously!" This is why acknowledging the feelings is so important, and this is why the approach to their acknowledgment must be delicate. The subconscious, emotional aspect of ourselves is fully aware that its beliefs are unfounded and illogical. All it is looking for is a recognition of its feelings of helplessness and lack of control. Then it needs to be gently shown how the distressing issue can be dealt with and brought within the safe boundaries of some semblance of control. This does not per se mean that it needs to actually be actively manageable, but it is to say that it needs to be emotionally manageable. This could be through an acceptance that everything is from Hashem and all that occurs is truly for our best, though we may not be able to see it at the time. It could also be that, in our overly emotional and distorted state, we overlooked a way that we can actively better our situation. This awareness of the ability we have to actually improve our situation can also have a positive effect on our emotional state.