marriage and marathons

marriage is an endurance race
perhaps the most difficult endurance race I have ever experienced

so often I will encounter someone in a relationship
they live with their significant other and well...
when I say I am married
they say they are not married, but that they live with their significant other and that it pretty much the same thing

a marathon is a race
26.2 miles is a distance
by running 26.2 miles you have not run a marathon
you have run a distance
it just is not the same thing
similar
but different
why is it different?
I do not know
it just is