A Daruma doll is in fact a tumbling doll (roly-poly doll) and because it always comes back to the initial position, it symbolizes Bodhidharma's persistence in meditation and the fact that he always reaches his goals. So the tradition is that after you buy the doll, you must make a wish and paint an eye - the left one. After the wish is fulfilled, you paint the second eye, then you bring it back to the temple, where it is burned at the end of the year (as customary with most of the Japanese lucky charms).
Visiting the Shorinzan Daruma Temple in Takasaki, Gunma - the place where the very first Daruma doll was created - I discovered an amazing collection of fulfilled wishes Daruma dolls, all brought to the temple. Actually the lady was just bringing one more:
EXIF info:
Nikon D90
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 20mm
Aperture: F/5.6
Shutter Speed: 1/125s
ISO Sensitivity: ISO 200