Every thing stopped. The announcement came over the intercom right after lunch, we were immediately sent home from school - we left class, went to our lockers, and walked home in what I recall as nearly complete silence. Television and radio programming concentrated entirely on every aspect, every detail of the tragedy and subsequent events. The most comparable experience I can think of would be the 9/11 attack in NYC. Every thing stopped.
The assassination changed every one who experienced it. It is often referred to as a loss of innocence, although I'd call it a loss of naivete. No matter what we have learned since, especially about the private lives of the Kennedys, what turned out to be a series of assassinations (JFK, RFK, MLK) completely disrupted and coarsened the culture.
We cannot forget because we suffered its trauma.
It is good to remember the dead.