There is the internal potency and the external potency, and in between these is the marginal potency, which has a connection with both the internal and the external potencies. The jiva, the real self, is the eternal servant (nitya-dasa) of the Supreme Person Sri Krishna and is the outcome of the marginal potency (tatastha-sakti) of the Supreme Lord. A vertical line can be diverted to either side, and also a river can be diverted to the sea. Similarly, when we become averse to Sri Krishna, the external potency envelops us and brings us to this world to pass through cycles of birth and death. If we have the desire to obtain emancipation then we have to cross over that marginal potency and enter into the internal potency. We have to submit to that internal potency, the superior potency. To get that which is superior, we have to submit. That concrete form of the superior potency is the suddha-bhakta - sad-guru. If anyone submits to the sad-guru, he will become blessed and enter into the internal potency. By entering into the internal potency we will get the transcendental, sweet, spiritual realm of Vaikuntha, Vrindavana, etc.