We will explain a bit deeper—for we aren’t talking here about a mere segulah or a cute vort, but about a major yesod: When the tefillah of a person is of a high caliber, the way it should be, there is no doubt that it will bring shefah to the person. But it is not simple for a person to attain a level where his tefillah is perfect.
When a person davens, and all his energies in tefillah are invested for him to achieve the thing that he wants, that alone arouses the מקטרגים—for they will say that he’s unworthy. He won’t necessarily be denied his request, but the מקטרגים will cause the conduits to be constricted. They will say, “You want to have this or that... what makes you so sure that you’re worthy of it?” And the moment a person is judged, the matzav is already not simple...and we need great siyatta diShmaya in order for the shefah to reach us. The less a person dedicates his tefillos to insisting on the things he wants, the power of the מקטרגים will be diminished.
We know from the sefarim hakedoshim that when a person davens for the sake of the Shechinah—that It should be spared from pain—his tefillos are far more potent. The problem is, in most cases we aren’t on the level to feel the pain of the Shechinah enough. The reason that such a tefillah is more potent and preferable is because a person takes himself out of it... he doesn’t insist on this shefah coming to him. The more a person places himself and his needs and desires into his tefillos, the harder it is for the shefah to reach him. Thus, as noted, tefillos on behalf of another person will be much more effective.
