The Upanisads say that he who says he knows Brahman does not know Brahman. He who says he does not know Brahman knows Brahman. We are all students forever. Sri Caitanya is Krsna trying to understand himself!
Still there is certainty within the mystery of the larger uncertainty/mystery. It is certain that our biological/physical self will come to an end. It is also certain that consciousness is not physical. Consciousness is an inconvienent truth for scientific materialism/physicalism, without which there would be no science, physicalism, nor materialism.
Consciousness is experiential existence. The limits of its experience are uncertain, in that even the experience of prema is full yet ever expanding. But the fact that it is existence itself means that is not subject to nonexistence. Because it belongs to a first person subjective ontology, it is not part of the third person ontology that makes up the objective physical world. That objective world is within time and space and thus all manifestations of it are limited by time and space. But consciousness not being contingent upon the objective world is thereby not limited by time and space. If is not physical, it is not governed by physical laws or constraints. And is certain that it is not physical. That which is subjective is not objective. You can’t get subjectivity from objectivity. But logically objectivity is derived from subjectivity. Again, there is no possibility of “materialism” without consciousness. The idea that there is only matter is just that: and idea belonging to the subjective world.
Thus while it is certain that our physical biological bodies have a beginning and end, it is also certain that our existence that is not bound by physical laws, time and space–consciousness–has no beginning and no end. So we should be certain that the mystery of life lies in the exploration of consciousness. And Gaudiya Vaisnavism is all about such exploration, providing a map down the road to prema.