May come and go. Gilbert's syndrome is a benign condition that affects the way your liver breaks down the hemoglobin from your red blood cells. In times of stress of illness, there may be some yellowing of the skin or eyes but this will not necessarily always be present. If it is persistent, it would be worth checking in with your doc to make sure something else isn't happening along with the gilbert's.
Improve liver. If your liver function can be improved the yellowish appearance to your eyes will also improve.
Yes. Jaundice from gilbert's can be exacerbated by sleep deprivation, prolonged fasting, and acute illnesses. Try to gets plenty of sleep eat frequent small meals, and avoid stress if possible.