I believe there are many paths to achieving tantric enlightenment. But, in the end, there are two main goals, complete openness to another and, within that openness, perfect balance. When these two goals are achieved, a true tantric union can formed. I'm going to get a bit sciency here because I think the quantum world can give us some insight on these two goals.

There are extraordinary features in the quantum world that have no analog in the world as we perceive it. One is superposition, being in two mutually exclusive states at the same time. a photon can be a particle or a wave. An electron can be in either the spin up state or the spin down state. These two states are analogous to you being inside or outside. With our generally accepted understanding of those two terms, it is impossible to be both inside and outside at the same time. Yet, electrons are small enough that quantum effects can manifest themselves. It is possible for an electron to be in a superposition of both spin up and spin down states, whereby it is simultaneously in both states. Once in superposition, an electron stays in superposition until something expects it to be in one state or another. At that point, the electron becomes either spin up or spin down, often at random. It's as if you can be inside and outside at the same time. Only when someone rings the doorbell do you find yourself inside the house ready to open the door or outside the house next to your visitor. This dropping out of superposition is known as collapsing the quantum wave function.

Another weird feature of the quantum world is entanglement. When two quantum particles in superposition become entangled, their fates become intertwined, no matter how separated they become in space and time. Should one particle fall out of superposition, so will the other, instantaneously, despite possibly vast distances between them. The two particles end up in the same state or opposite states, depending on the type of entanglement. Einstein, who was not a big fan of quantum theory, called entanglement "spooky interaction at a distance".

The quantum world is a good metaphor for a tantric experience between two people. To achieve tantric bliss, each person must be in perfect balance, a superposition of yin and yang, of giver and receiver. One person cannot be just a giver. One person cannot be only the receiver. One person cannot have power over the other. One person cannot be subservient to the other. Moreover, both people must be so open to each other that they become entangled, their fates intertwining. When some outside calling causes the experience to end, when the tantric wave function collapses, those in the tantric union will be forever touched.