The Washington Post dives into a theory originally put forth by Paul Janet in 1897: We perceive the first years of our lives to be much longer than the years that come later because our point of reference for time is smaller when we're younger.

When you've only lived four years, one year is a big chunk of time — it's 1/4 of your life!

But when you're 70, a year passes in the blink of an eye. So even though we all get the same 24 hours in every day, it goes by faster and faster as we get older.

That begs the question: What are we doing right now to set ourselves up for a life lived to its fullest as it increasingly seems filled up?

What do you want to look back on when you're 75? What decisions will make you proud? What's the life you want to have lived?

We can do our best to "plan" our lives, but often, even the best laid plans fall apart or evolve into something you couldn't even have imagined.

Still, there are basics we know we can't escape: Food, water, and shelter are things that we all have to plan and prepare for, regardless of where life's road takes us.

So, what can you do today to prepare for a life that you can only loosely predict? Here are five ways to think about it.

What do you consider to be successful? It may be one thing or it may be a combination of things. Either way, defining what success means to you can help you identify what you'll need to achieve in order to believe you lived a "good" life.

Once you know what makes you happy, build on that. Formulate an idea of where you'd like to be in 30 years so that you have a direction to start moving in. Money blogger, Finance Girl, puts it this way:

Having a vision doesn't mean things will work out exactly as you'd planned, but it empowers you to act with intention. To move forward each day, working toward this larger ideal.

Sure, there are a million factors beyond your control that affect your life every single day, but remember that you do play a part in what happens. Ayse Birsel, author of "Design the Life you Love: A Step-by-Step guide to Building a Meaningful Future," says "your choices will determine the kind of life you are designing." As such, they should map back to your vision. You have to own them.

As you work toward your goal, be open to change. Don't hold onto things too tightly or life's turbulence will rock you.

Paul B. Brown, co-author of "Just Start: Take Action; Embrace Uncertainty and Create the Future" reminds us to learn each step of the way. He says, "Determine your desire. Take a small step toward it. Learn from taking that step. Take another step. Learn from that one."

Keep learning. Keep growing. Keep moving forward.

Think about the things you can control, the factors you'll need to prepare for regardless of your life's ever-shifting trajectory. Money is one of them.

You can put the wheels in motion now so that you're not worrying about your finances at 75. You'll want to have everything as buttoned up as possible long before you're asking yourself where did the time go?