How can one minimize sleeping hours as much as possible without harming oneself, knowing that a large part of the day is spent at work and commuting?

Excessive sleep hardens the heart and wastes time, whereas less sleep enables the servant to perform acts of worship. The Salaf (pious predecessors) considered excessive sleep an illness and reduced it, citing the Almighty's saying: "They used to sleep but little of the night."

To reduce sleep without harming oneself, the following are recommended: 1. Reducing food intake. 2. Gradually reducing sleep hours. 3. Distributing sleep over periods, with a preference for a siesta (between Dhuhr and Asr) and a prohibition of staying up all night. 4. Fear of Allah and devotion to worship; for fear reduces sleep.

One must define the purpose of staying up late before reducing sleep, such as dedicating time for study or worship. A student stays up for his studies, and so does a seeker of the Hereafter.