There is a good chance this is how you will feel at the peak of a
psychedelic experience. (See
LSD,
Psilocybin.)This state can also be caused by a good cup of
coffee or swimming in a cold
river cradled in the arms of an overflowing
rainforest.
Note: the realisation that this expression describes your state of mind is often followed by the uncontrollable urge to tell the world about it, in no uncertain terms, and at no gentle volume.
Sleeping neighbours may have mixed feelings about this effect if it takes place during socially unacceptable hours.