my experience with this is when my mind is left alone absent of emotions.

physiologically the brain will not function unless the heart pumps blood to it.

must have a spiritual aspect?

shut the emotional heart down and the brain goes into waking coma...

thats why it's hard to think with depression cos feelings are subjugated by the other parts of the body manifesting into back aches neck aches fatigue loss of apetite clumsiness and injuries some fatal and on purpose.

the heart wants to save the brain the brain wants to be fed the heart is empty the mind has to watch all this and it improvises screening within black and white fuzz.

bipolar mood swings make this such a regular event and health can fluctuate daily it's astonishingly 'full on'

gotta wait can even encourage the escape...back to vibrant colours...gotta feel something something that the heart can enjoy to invigorate the mind

it's simply....being in anticipation of something better or actually experiencing IT right then and there!

different for everybody but the same principle

(sorry for a long reply here just relate)