What we think we perceive.
Perception is the interpretation our brain makes based on what you see, hear, smell, feel, taste and the information that is already stored within our memory.
Sensation refers to the process of receiving information through the senses, perception refers to the way our brain interprets these sensations.
Now, no one person can see all the angles in situations, we are all fundamentally handicapped and base our presumptions on what we "thought" to be accurate analyses of whats going on at any given moment.
However, i find the malleability of people living with dementia can be a big proponent in there ability to experience a more gratifying moment to moment experience and not spike all those stress fulled, brain juices that we create when frustrations and stress begin to set in, due to holding on to a preconceived idea, thought to be a fact.
Life's a slow ride, so in the wise words of Foghat, slow down, and take it easy. (we're better off).