On day, as Ra was in his older years, mankind had begun to mock Ra and planned to overthrow him from his throne of power. Ra got very angry and worried so he went to the other Netjeru and asked for their advice. The other Netjeru (one is sometimes mentioned.. Nun..) as having advized Ra to punish the blasphemers. Ra took them up on his advice and chose the best Netjeret for the job. He used one of his eyes, his daughter Het Hert in the form of Sekhmet to do his bidding.

After awhile, Het-Hert had developed quite a taste for blood and by the time Ra had decided that enough punishment was had, Het-Hert couldn't stop. She kept on her savage slaughter of all of humanity. Ra took pity, as he only wanted to punish and not wipe out mankind. He again sought the help of other Netjeru and decided on a plan to trick Het-Hert. He gathered up a bunch of red ochre and filled up seven thousand jugs of beer mixed with the red ochre and spread them out on the next field that Het-Hert had planned to destroy. Het-Hert was of course asleep and resting, unaware of the plan that Ra was carrying out. When Het-Hert next woke up, she took the bait and drank up all the beer thinking it was blood. She fell into such a drunken stupor that when she finally came out of it, she had forgotten her original intent and was once again the benevolent and loving Netjeret she is known as.

There are many variations on this myth, but you will find that they all go somewhere along these lines.

Sekhmet also has healing powers and is sometimes shown as a protecting mother figure. Sekhmet is mostly seen as having the head of a lioness and the body of a woman. Usually she wears a skirt from the waist down and her hair (or a necklace or collar or sometimes nothing) covers her breasts. Also, her clothes are normally red or its compliment green, and she is usually shown wearing a lapis and gold necklace or collar. Since she is very powerful (her name literally means "Powerful One") she is usually shown as sitting down on a chair or walking (she is very active). Sekhmet is the wife of Ptah and together their son is Nefertum. In later kingdoms Imhotep was seen as the adopted son of Sekhmet and Ptah. Imhotep was dieified in later kingdoms for his great knowledge. Imhotep was the architect for the very first pyramid in Egypt (first as in by putting more layers on top of each other and great in size) known as the Step Pyramid in Saqqara, built for Pharaoh Djoser in the Old Kingdom.

-Tomb of Senet, Middle Kingdom
Parkingson translation