Taking a withdrawal from a 401 (k) before age 59 and 1/2 typically results in a 10% penalty. If you leave your job at 55 or later, you may be able to take earlier 401 (k) withdrawals penalty-free.

Of course, there are some downsides. You don't get to take advantage of capital losses, which can be used to offset gains in a taxable account. You also have to pay taxes on withdrawals from 401 (k) ...