Modify Savegame
     First,  play  the game and grab HAPPY essence (because it is easy
to  obtain)  or APPLE (because it is the first essence), then save. Go
to  My Documents folder -> Electronic Arts -> Mysims -> SaveData1 (can
be  1,2,3 according the savegame number). Open playerRecord.xml with a
text editor such as Notepad.

Find the line:

<happy type="number"> (or <applefruit type="number"> )

In this line you can edit the number of essense (up to 99) for example:

<happy type="number">99</happy>
<applefruit type="number">99</applefruit>