At 40 I had to take some steps to stop my 401K from evaporating. For the last 17 years the diversification of: 30% US stock market, 30% Global equities, 20% growth ( the riskiest one) and 20% Money market, was not perfect, but worked just fine. When one goes down the others somewhat moved in the opposite direction. That worked until last year, when all the funds started moving down.
Once Bear Stearns failed earlier this year with clear signs that more speculators to follow, I decided to borrow as much as I could from my own and my wife's retirement plans. Put the procedes into our joint savings account. We are paying back, but we are paying back to ourselves, we are paying interest to ourselves and thus we are replenishing our funds by buying securities at lower prices. If we did not do this, since April our retirement funds would have lost 9%. The key is not to spend the money you borrowed from yourself.