Anxiety about retirement is high — and rises with every shudder in the financial markets. Americans are increasingly worried that they won’t have enough money to carry them through their lifetime. They’re looking for advice on how to invest their savings to meet that goal. Most of them are investing in mutual funds. More than half the assets in retirement plans managed by individuals — think IRAs, 401(k)s and 403(b)s — are invested in mutual funds, according to the Investment Company Institute. Here are eight tips to help you manage your fund investments to keep your retirement savings on track.