  We study the connection between dissipation and reality in macroscopic
quantum systems. We present the following scenario; if we consider the dynamics
of a `partial' wave function, the dissipation is represented as a nonlocal term
and it causes destructive interference to suppress the quantum fluctuation.
Using the variational method, we confirm that this dissipation term is a
reasonable extension of the standard (Schr\"odinger) description for isolated
systems, from which we also derive the classical action. Consequently, in
macroscopic systems, the states whose time-integrated dissipation takes an
extreme value come true. This description, which is consistent with our sense
of reality, coexists with the usual linear-time-dependent description.
