We know time is constant yet we perceive that time speeds up as we age.  But why is this so?
1- The ever growing measuring stick. For a 5 year old 1 year represents 20% of their life but to a 50 year old it is only 2%.  This is simply an internal scale of relativity.

2- Biology of decay.  We lose elasticity in our brain tissues as we age, causing neurons to fire less rapidly.  Our slower physical processes create the false paradox of faster time.

3- Memorable equals measurable.  Graduation, first kiss, first car, prom, first job... all memorable events crammed into a relatively short time span.  Memorable events occur less often as we age therefore giving us fewer book marks.  

4- We pay less attention to time.  In 6th grade you may have looked at the clock every 5 minutes in anticipation of getting out.  On December 1st you may have been eagerly awaiting the arrival of Santa Claus.  But as an adult December 1st is just another day at the office with your time already allocated.  When we become engrossed in mundane tasks we simply do not take time to notice the passage of time.

5- The stress-time factor.   Adults often feel that there isn’t enough time to accomplish their tasks (stress) which can cause the brain to interpret this as time passing more quickly.

While diet and exercise have some impact delaying the biology of decay the remaining factors can only be modified through the psyche.  In other words...  it’s all in your head.  ;) 

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