I think what you mean is that the two sides of the coin, or the two river banks, are parallel to each other, and there are many parallels to, and in, life. And what I mean by parallels is that they could be literal or metaphysical, tangible or intangible. Without getting technical or into true physics, which I know nothing about, consider these:
For every up, there is a down.
You get what you give.
The grass is not greener on the other side, it's greener where you water it more. (Think about that one, you'll understand what it means.)
Kindness and smiles are contagious.
The "Pay It Forward" concept from the Kevin Spacey/Haley Joel Osment film.
For every action, there is an equal and opposite reaction, but that doesn't mean necessarily that it will happen.
Things in motion tend to stay in motion, things at rest tend to stay at rest. (Consider this: Someone who is unemployed and sitting at home on their rear all day will not just have work find them. If that person decides that day is their day to change, and they get out there and start job hunting, and they work hard at it, they're bound to find some kind of work.)
Those are just some things for you to consider. Hope my answer helped you and that you have a great rest of the week!