I think, that multiple psychological reasons cause the blocking, like fear, stress, past memory, fixation on certain syllables, etc. All of this leads to physiological responses, like muscle spasms, breath modification, etc. Then, in attempts to break this vicious cycle we are trying to correct those involuntary physiological responses, e.g, relax the muscles, change the breath, which eventually produces a desirable outcome. The "tricks" can help to break off bad psychological loops , i.e. disable them.