Many factors are involved in the development of fatigue in transportation, as discussed previously in other chapters. This chapter proposes to present lifestyle as a mediator of fatigue among professionals working in this sector. First, we distinguish between fatigue and sleepiness and present their definitions. Then, we show examples of lifestyle factors that can contribute to fatigue. Finally, we discuss how society is driven to determine lifestyle. At the end of the chapter, some final remarks put together the factors presented and how they can act together.