You will want to take precautionary measures to protect your feet from extreme heat or cold. For instance, never walk barefoot or with sandals on hot pavement, beach sand, etc. Since you might not have feeling in your feet, you will not know if the hot surface is causing a burn or any other damage or injury.
On the contrary, in cold temperatures, you will also want to protect your feet. If you are aware that the temperature is very cold, go ahead and put on some wool socks and/or any other items known to keep feet warm. Once again, the lack of sensation may keep you from protecting your feet, leading to damage from the cold temperatures. Since blood circulation is already poor, you cannot depend on your body to send warm blood to your feet and the cold temperatures may increase nerve damage.