It's amazing how easily fear overcomes resolution, and how easily long-term investors turn into panicked sellers in a market decline. That's what happens when you don't have a plan that you understand, and a commitment to stick to the plan. Words like "diversification" or "asset allocation" seem to come from a different language. But the falling balances in your retirement account are unmistakable signs that your chances of retirement are going down the drain. Don't panic -- and don't rely on historic facts, even the ones I've often given. True, over the long run, there has never been a 20-year period where you would have lost money in a diversified portfolio of large-company American stocks with dividends reinvested. Facts are cold comfort without a plan. Do you have that 20-year "long run" to wait, and the discipline to hang in there? Or do you need some of your portfolio in safe, "chicken money" alternatives that will let you sleep at night? Even in the midst of a market decline that could be protracted by an oncoming recession, it's not too late to make a sensible plan. Here are three sources of reliable advice -- and they're at your fingertips. Retirement Calculator Mutual fund giant T. Rowe Price ( TROW) has just introduced a new and improved online retirement investment and income calculator. You'll find it at www.TRowePrice.com/RIC. Using sophisticated "Monte Carlo" modeling, it takes the information you input about your desired retirement age, current income, hoped for retirement income, and your current amount and rate of savings, to give you a realistic assessment of how far short of your goals you're likely to fall -- and how much more you need to save. The calculator will also recommend appropriate portfolio asset allocation between stocks, bonds and safer, short-term investments to help meet your goals.