Many people are convinced that what they practice must be of supra- mundane nature. How can it not be if they have been practicing the five extraordinary preliminaries? In fact, these five preliminaries are not only supramundane in nature but also part of the Mahayana practices. The key is, notwithstanding, having what kind of perspective when you sit down to practice these preliminaries. Though the possibility of practicing solely for the benefit of this life is slim, it is quite likely to undertake these practices to avoid rebirth in the hell realm. If the motivation is not to seek liberation for the sake of all sentient beings, the practice of the five preliminaries will be considered mundane, not supramundane. 

- Quote from The Right View, "The Three Differences"