According to research from the Fidelity Investments Retirement Savings Assessment study, 84 percent of respondents wonder whether they will be able to afford health care in retirement, but 71 percent expect to have better-than-average health in retirement, an overly optimistic assumption for many, the report found.

Many Americans greatly underestimate the amount of savings they may need to cover health care costs in retirement. A study last year of pre-retirees (ages 55-64) found that nearly half of respondents believe they will need about $50,000 to pay for their individual health care costs in retirement. Fidelity's annual Retiree Health Care Cost Estimate, which has estimated the cost of healthcare in retirement every year for more than a decade, has found that the average couple could expect to spend more than $220,000 in healthcare expenses over the course of their retirement.

Many individuals don't understand the long-term financial impact that making positive health decisions can have.  When asked which resolution is more important to keep—financial or physical fitness—a recent Fidelity study revealed that 53 percent of respondents prefer to keep financial fitness resolutions, compared to 43 percent opting for physical fitness. They don't realize the significant connection between the two—and the importance of focusing on both—especially when it comes to health care costs in retirement.