Make sure there is a bed by the wall. Put your Sim to bed and after they are asleep, go into buy mode and put something in the way of them from getting up. Return to live mode. Click on something such as going to the bathroom or sitting on a couch. They will try to get up, will not be able to, and lay back down. Then, go back into buy mode and move the item. You can now go back into live mode and be sleep walking. To check on this, click on yourself and it should read "Wake up". This will help keep your fun, energy, and social levels up. However, stay away from noises like radios, computers, and the television. Also, do not take a shower or you will wake up. You cannot do transactions with another Sim in this condition, but can do whatever you want.