If you don't receive the maximum matching contribution, it's like turning down free money. Make sure you know how your company match works, and take full advantage of it.
Human nature makes it easy to take risk when the market is doing great.
Conversely, we are more apt to bail out after something bad has happened. Following our emotions, many of us would buy high with enthusiasm, and then sell low in a panic. Better than a hunch or even an educated guess, determine the right mix of investments for your temperament and goals and stay with it. You'll have good years and bad, but you will also be more likely to earn the average historical return on stocks, which have outperformed every other investment category. If you are close to retirement you may want to take a more conservative approach.