The one thing that I routinely come across in regards to health is how little the average person understands about how time affects the occurance of Chronic Disease.  The term "chronic" relates to time. 

Most average people, mistakenly believe that Chronic Disease is disease that occurs as we age.  This mistakenly leads people to believe that aging and disease are synonymous.  To be old is to be sick. This model of disease completely ignores the effect of a person's health behavior over that aging time.

The theory I subscribe to states that Chronic Diseases are the product of either positive or negative health behaviors over time.  In short, if you have good health behaviors you'll be less likely to develop a Chronic Disease.  Bad Behaviors will make it more likely for Disease to occur.  This model states that while time is a factor in developing a Chronic Condition, it isn't the only one.

Chronic Diseases progress slowly over time and factors like lifestyle and too some extent genetics play a role.  As for which is the more powerful force I think the argument is a False Dilemna.  Both interact and both are significant.  Since Medicine is currently ignoring lifestyle as a factor they are leaning towards genetics.  I believe that how we live determines which of our genes get expressed.  That means that you may have a gene for Breast Cancer, but if you live healthy enough you won't get it, etc.

The "Age = Chronic Disease Crowd" would have you believe that it is genetics alone that determines sickness.  Because, for one thing, they have many Genetic Researchers that need grants and so they have to hype it as much as possible.  Genetics alone can't account for the huge change in the Chronic Disease profile of the United States.  Mutation and genetic variation does not happen that quickly.  What we are looking at are Negative Lifestyle Issues.

If we make bad choices they negatively affect us.  If we routinely make bad choices over time, then we're pretty much earning ourselves a Chronic Disease.  Time is a magnifier of bad health behavior.  Do something wrong once, no big deal.  Do something wrong as part of your daily or weekly routine, we've got a problem.  That error in judgment will repeat itself over and over and over, creating a huge negative impact on a person's health.  If you eat McDonald's everyday for lunch, BIG IMPACT!  If you eat it every so often, no big deal.

Gradual and Silent
Chronic Diseases seem like they just show up, but they don't.  They silently worsen over time.  Ask yourself what does 1/100th of a Heart Attack feel like?  Nothing.  What about 3/100ths of Breast Cancer?  Nothing.  The problem is that many of the Chronic Diseases can be prevented if we practice the right Health Behaviors long before it has become a life-or-death scenario.

Don't count on your own health observations either.  The changes in the person's health can happen so gradually that a person may have gotten used to them and discounted them.  If you place a frog in a boiling pot of water it will hop out.  However, if you place one in a lukewarm pot and slowly bring it to a boil the frog will stay in it until it boils and it eventually dies.  Kind of a graphic example, but I think you get my point.

Your health doesn't decline in one big event.  It declines second-by-second, minute-by-minute.  It also improves second-by-second, minute-by-minute.  The little things we do each day DO MATTER!  You eat McDonald's once a week or once a day it has an impact.  You smoke, ignore your bodies need for sleep, don't manage your stress, don't workout...and so on.  It adds up!

Doing these things individually will not, most likely kill you right away.  But they do have an effect and that effect is magnified over time.  Time causes small mistakes to be magnified to become something large.  A small error that costs you an extra minute or two each day adds up to be significant in the course of a year (6.08 hours to 12.16 hours/year lost).  The same error in how you eat, drink water, exercise, supplement, sleep, destress and so on adds up also.

Edit Your Daily Routine
Take some time and write down what you would consider a routine day for yourself.  Are there things you do or don't do each day or week that could be slowly leading you towards a Chronic Disease?  How might you alter or change these behaviors so you're making healthier decisions?  If you've been conditioned to be unhealthy, start retraining yourself.  Change your programming.  Figure out why you do certain things and find healthy alternatives to it. 

The boring little things you do each day DO MATTER, especially over time.  Good luck!