Few people can accurately time the market; buying at the lowest point and selling at the highest point is nearly impossible on a long-term basis. When you invest in mutual funds with diversified portfolios, timing the markets can be even tougher. Tracking the prices of your mutual funds (or other investments) on a daily basis is time-consuming and can also cause you to lose sight of your long-term goals. Checking your investments on a weekly or even monthly basis might make better sense – that way you won't be as likely to give in to emotional trading or to panic during short-term dips in fund performance.

Consider buying or selling your investments when they no longer meet the criteria you have established; if an investment performs poorly for a long period of time, or if a fundamental change in the economy takes place, then buying and selling could be a good option. Just don't look at your investments too closely or too frequently; your goal is to grow wealth over the long term.