Even though virtual particles are created and destroyed, there is always a symmetry to the process. There is a time symmetric, mirror-like quality to every interaction in the early Universe. Symmetry also leads to conservation laws, and conservation laws limit the possible interactions between particles. Those imaginary processes that violate conservation laws are forbidden. So the existence of symmetry provides a source of order to the early Universe.
Pure symmetry is like a spinning coin.
The coin has two states, but while spinning neither state is determined, and yet both states exist. The effect of symmetry breaking in the early Universe was a series of phase changes, much like when ice melts to water or water boils to stream. A phase change is the dramatic change in the internal order of a substance. When ice melts, the increased heat breaks the bonds in the lattice of water molecules, and the ice no longer holds its shape. Phase change in the early Universe occurs at the unification points of fundamental forces.