Make all happy
If any of your sims are feeling down all you have to do is type in ctrl shft and c to get on to the cheat screen. Once there enter: testingcheatsenabled true. Then just shift-click your mail box and among other things, one option will be 'make all happy'. All your sims will suddenly be real happy (unless of course a member of the family has recently died, they've been cheated on, and they were just dumped. Then they have no hope and will probably commit suicide.
Added by: Cheats Always Pr.. Aug 3rd 2011, ID#16446