There is another component to why magic works. This is the component that is frequently upheld as the primary modus operendi of what is the functional working bits of magic. It is also what skeptics and others point to and use to declare that all of magical study is nothing more then psychological manipulation of the gullible. This argument, however, is ignoring the other (previously discussed) elements of magical study.
The major component to how magical efforts work upon the psyche is hypnosis. Generally, it is some form of self-hypnosis. The induction of trance has many different methods, which will be discussed in greater detail in their own post, and the goal is to enter into an altered psychological state which renders one's waking self more pliant to suggestion. Once in this altered state, one is able to implant commands for oneself to execute in a given setting, access intuitive spiritual knowledge, or focus their thoughts intently upon a magical goal.
The most common use of the hypnotic state in magical studies is the third focus. In solitary witchcraft, the process is quite similar to implantation of commands. When one is engaged in practicing witchcraft with a coven, the person who is leading the ritual (in most Wiccan covens, this is the High Priestess or High Priest) pays close attention to the spiritual energy level of the group and their depth of trance. When all has arrived at the correct intensity and depth, the person leading the spell gives a signal for the coven members to direct their spiritual energy and thoughts towards their goal.
A large amount of magical study has been focused upon how one becomes more integrated in their personality, heal psychological wounds, and to bring about a general sense of health and well being in one's life. It is highly advisable for one who is engaged in this sort of magical undertaking to acquire a basic knowledge of psychology. It is also exceptionally important for one to be brutally honest with themselves. Self deception serve to undermine one's magical efforts and will either result in no progress made or harmful developments.
Some witches find that practicing alone is easiest and provides the most efficient way to address questions of one's psychological well being. It is rare to find one who engages in such work and does so with out any external supports. These supports can come from not only the witchcraft community (as happens with most coven work) but also from professionals in the health community, well meaning associates, and a great deal of research into one's own psychological state. To be trite, knowledge is power.
The power that comes from the basic knowledge of psychology is the ability to use trance more effectively, circumvent self deception, and to have a working understanding of how the mind operates. This can lead to more effective self-regulation of mood and mental state. It can also lead to improved communication with others. If one finds themselves in the position of providing spiritual or emotional assistance to another, this not only helps to make one more effective at doing so, it also makes it easier for one to determine when the situation is beyond their expertise.
The secondary psychological component that is behind successful magic is accurate assessment of one's psychological strengths and weaknesses. This type of self knowledge enables one to tailor their spell craft to work with their unique personality. Spell craft that is designed to take into account the strengths and weaknesses of the spell caster is far more effective then something that is crafted for any general user. (This is why personalized spells are preferred as a general rule.) It is the equivalent of having a tool that is designed to fit your hand versus one that is just off the shelf for any person to use. It enhances the effectiveness of the tool and make the tool more comfortable to use.
The third element to be considered is the suspension of disbelief. In our daily lives, we are regularly encouraged to focus upon what is only perceivable by the classical 5 senses (sight, taste, touch, sound, and hearing). To have any sort of publicly espoused belief in some alternate senses is to find oneself in a most uncomfortable position scrutiny and scorn. As such, disbelief in any possible psychic talent that one may have become habitual and a self-fulfilling prophecy in extreme cases. In the case of people who have latent psychic talent, the continual message that they are living in a fantasy, mad, or acting childish is detrimental to their health and well being. Indeed, such things can be enough to render said psychic person blind to their own talents.
The suspension of disbelief in things ranging from ones' psychic talents to spiritual beings (ie fairies, dragons, or angels) gives one permission to use these abilities and to access their spiritual nature. This, in turn, helps one to align their thoughts and will into greater focus upon their goal. Thus, proving to have a higher magical success rate.