An adage that, referring to the risk/return trade-off, says that the type of security an investor chooses depends on whether he or she wants to eat well or sleep well.
Investing in high-risk, high-reward securities will offer you the potential to eat well, but the risky nature of these securities might prevent you from sleeping at night. By contrast, investing safely means that you will sleep well, but the low rate of return may keep you from eating well.