You must learn energy conservation. A 100 watt bulb is fabulous for particular tasks, but uses a lot of energy and is unpleasantly bright. Constantly working at your outer limit is not sustainable; you end up burned out. 40 watts gives a warm and pleasant illumination for most activities and conserves energy as well.
Practice working at 40% most of the time and turn on the 100 watt bulb only as a task light. Consider ways to conserve energy in your life.