The Trill Humanoids share their planet with a wormlike oceanic life form which originated in the deep purplish oceans of Trill. Unlike the Trill humanoid life forms these oceanic life forms could live for well over a thousand years.
What made this planet and its inhabitants unique was their unique relationship with each other. You see, the wormlike oceanic life forms of Trill could exist in the deep oceans of Trill where they enjoyed a simple and long life or they could exist in a symbiotic relationship with the Trillian humanoids being their host.
The symbiotic relationship allowed the symbiotic life form, which would out live its host, to carry its knowledge, memories, and skills from host to host for over a thousand years giving each new host a greater ability and opportunity in life. The only catch is that once the symbiotic relationship was established it must be maintained because if the symbion were to be removed from its host it could not survive on its own. This symbiotic relationship had to be an abiding relationship, because the symbion gained its source of existence from the host. Outside the host it could do nothing.
So it is with our relationship with Jesus Christ. Once we are born again we enter into a spiritual symbiotic relationship, if you will, with Jesus Christ.