  We present a toy model for the thermal optical/UV/X-ray emission from tidal
disruption events (TDE). Motivated by recent hydrodynamical simulations, we
assume the debris streams promptly and rapidly circularize (on the orbital
period of the most tightly bound debris), generating a hot quasi-spherical
pressure-supported envelope of radius R_v ~ 1e14 cm (photosphere radius ~1e15
cm) surrounding the supermassive black hole (SMBH). As the envelope cools
radiatively, it undergoes Kelvin-Helmholtz contraction R_v ~ t^(-1), its
temperature rising T_eff ~ t^(1/2) while its total luminosity remains roughly
constant; the optical luminosity decays as nu L_nu ~ R_v^2 T_eff ~ t^(-3/2).
Despite this similarity to the mass fall-back rate Mdot_fb ~ t^(-5/3), envelope
heating from fall-back accretion is sub-dominant compared to the envelope
cooling luminosity except near optical peak (where they are comparable).
Envelope contraction can be delayed by energy injection from accretion from the
inner envelope onto the SMBH in a regulated manner, leading to a late-time
flattening of the optical/X-ray light curves, similar to those observed in some
TDEs. Eventually, as the envelope contracts to near the circularization radius,
the SMBH accretion rate rises to its maximum, in tandem with the decreasing
optical luminosity. This cooling-induced (rather than circularization-induced)
delay of up to several hundred days, may account for the delayed onset of
thermal X-rays, late-time radio flares, and high-energy neutrino generation,
observed in some TDEs. We compare the model predictions to recent TDE light
curve correlation studies, finding agreement as well as points of tension.
