Being able to consistently contribute enough to your retirement savings accounts is the single most important aspect of any retirement plan, but it's also by far the most challenging. So finding a way to make regular, adequate contributions easier is really the key to a successful retirement. And the best way to accomplish this is by having a written financial plan.

Why does a written plan help?

Self-help gurus uniformly urge their clients to write down their goals, plans, and dreams for a reason. Writing something down has a significant psychological impact on the writer: It makes that written declaration more "real" to us and gives us accountability. Once it's in writing, we feel more compelled to follow through on it. For a task like saving for retirement, that feeling of accountability can make all the difference in sticking to a contribution plan versus having a plan but only contributing "when it's convenient." A written plan also motivates us by reminding us what we stand to gain tomorrow by sacrificing today.

Cash in envelope labeled 401k

Image source: Getty Images.

The power of written financial plans

A recent study by Charles Schwab Corporation highlighted the impact that written financial plans have on retirement savings. The study compared various financial attributes of Americans with a written financial plan to those who did not have one. For many important financial tasks, the difference between the two groups was startlingly high.

For example, 27% of savers with written financial plans maxed out their contributions to their retirement savings accounts, compared to 11% of savers without plans. Thirty-four percent of savers with written financial plans had investments in addition to their retirement investments, versus only 16% of those without written plans. And 49% of savers with written financial plans felt very confident in their ability to reach their financial goals, as opposed to just 13% of those without written plans.

Starting your financial plan

Financial plans come in many forms -- debt payment plans, down payment savings plans, investing plans, and so on. And while the idea of creating a financial plan may sound daunting, in reality such a plan can be extremely simple, as you'll see shortly. We'll focus on a retirement savings plan, but the principles are similar for creating any type of financial plan.

First, your plan needs a goal. For a retirement savings plan, the goal will typically be to save enough during your working years so that when you reach your planned retirement date, you will have enough money to live comfortably for the rest of your life. Because different savers have very different ideas of what "living comfortably" entails during retirement, the exact number you end up with as a savings goal will depend largely on your own preferences and situation.

In order to know how much money you'll need to save for retirement, you first need to figure out how much you'll be spending during that time. Ideally, you'll write up a list of the expenses that you expect to carry during retirement and add them up. If that sounds like too much work, you can get a pretty fair estimate based on your current income.

If you anticipate a fairly sedate retirement without a lot of fancy, expensive activities, you can assume for planning purposes that 80% to 90% of your current income will suffice as annual income during retirement. Aim for the low end of this range if you're sure you'll be debt free by the time you retire (that includes owning a home that's completely paid off). Otherwise, aim for at least 90% of your current income. On the other hand, if you dream of an adventurous retirement touring the capitals of the world, aim for at least 100% of your current income (or possibly even more, if you have really expensive plans).

Making it official

Once you have a goal for your retirement income, you can plug that number into a retirement calculator to find out how much you need to save in order to hit your target by your planned retirement date. Let's say that your goal is to save $1 million by age 65 and the retirement calculator tells you that in order to reach your goal, you need to save $1,000 per month. Write this down in a form that will inspire you to follow through. For example, you might write "Millionaire by age 65: $1,000 every month into the 401(k)." Then post a copy of this document somewhere you'll see it on a regular basis, such as next to your bathroom mirror, on the front of the refrigerator, or attached to the side of your computer monitor.

Just having the plan in writing, staring you in the face on a regular basis, can work wonders to improve your follow-through.