Accordingly, the soul of man, which is found in each and every world, must grow and complete itself from all the aspects found in that world. This is the third principle mentioned above: One must know regarding all the statements of the Zohar, every single detail from the lofty worlds it deals with, whether the sefirot, the souls, the angels, the clothing, or the palaces, even if it is discussing them on their own terms, the reader must nevertheless understand that they are stated mainly in reference to the measure that the soul of man that is there receives from them and is nourished by them. Thus, all its statements are focused on the requirements of the soul. If you comprehend everything along these lines, then you will understand and succeed in your undertakings.
Baal HaSulam's Guide to the Wisdom of the Zohar
Baal HaSulam's Preface to Zohar 21:3