Q. I know you have recommended that attending physicians should be putting about 20 percent of their gross income toward retirement. My spouse and I have found this to be very difficult, both early on and now that we’re in our mid careers. I am a bit embarrassed to say this, but I don’t see how we could spend much less than we currently do without a dramatic change in our lifestyle. What should we do?

A. Just as the time required to perform a chore seems to expand into the time available, so does our spending naturally expand until it consumes our entire income. For most people, it requires a conscious and sometimes difficult effort to avoid this process. It is also a truism of personal finance that decreasing spending is far more psychologically painful than increasing spending is pleasurable. To make matters worse, many of us find ourselves on the “hedonic treadmill,” also known as “hedonic adaptation.” As you make more money, your expectations and desires rise in tandem, resulting in no permanent gain in happiness. Thus, you work harder and harder, spending more and more, and then find you are no happier making and spending $500,000 a year than you were making and spending $100,000 a year. To make matters worse, the increasingly progressive tax burden on that additional income can further destabilize your finances.

Since you can always spend your entire income and then some, the secret to financial independence always lies primarily on the spending side of the equation. As a rule of thumb, financial independence means you have a level of assets that is approximately 25 times your annual spending requirements. The less you spend, the sooner you will become financially independent and the less you will have to save to reach that point, which also means you will need to take less risk with your investments. The easiest way to avoid the hedonic treadmill is to never get on it in the first place. However, for most of us, a conscious effort is required to get off the treadmill or at least limit its effects on our financial lives.

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Financial literacy can pay great dividends in this respect. If you have never heard of hedonic adaptation, chances are that you are already on the treadmill. Recognizing this completely natural tendency goes a long way toward fighting it. Understanding the consequences of a low savings rate (ie, out-of-control spending) is also helpful. Saving more money each year not only increases the size of your nest egg, it also reduces the size of the nest egg required to maintain the same lifestyle in retirement. The math behind financial independence is surprisingly simple. You can make a chart with a 0 percent savings rate at one end and a 100 percent savings rate at the other. Then using some simple basic assumptions (ie, 5 percent real investment return and a 4 percent real withdrawal rate) and ignoring the effects of pensions and Social Security, you can determine how long you need to work for any given savings rate.