Suicide, like any other murder is a sin because it is a sudden disturbance of the harmony of the world... Nature exists for the sake of the soul and … - William Quan Judge

The fate of the suicide is horrible in general. He has cut himself off from his body by using mechanical means that affect the body, but cannot touch the real man. He then is projected into the astral world, for he has to live somewhere. There the remorseless law, which acts really for his good, compels him to wait until he can properly die. Naturally he must wait, half dead, the months or years which, in the order of nature, would have rolled over him before body and soul and spirit could rightly separate. He becomes a shade....

Patanjali's rules compel the student not only to acquire a right knowledge of what is and what is not real, but also to practice all virtues, and while results in the way of psychic development are not so immediately seen as in the case of the successful practitioner of Hatha Yoga, it is infinitely safer and is certainly spiritual, which Hatha Yoga is not. In Patanjali's Aphorisms there is some slight allusion to the practices of Hatha Yoga, such as "postures," each of which is more difficult than those preceding, and "retention of the breath," but he distinctly says that mortification and other practices are either for the purpose of extenuating certain mental afflictions or for the more easy attainment of concentration of mind. In Hatha Yoga practice, on the contrary, the result is psychic development at the delay or expense of the spiritual nature. These last named practices and results may allure the Western student, but from our knowledge of inherent racial difficulties there is not much fear that many will persist in them. (Preface)

2. Concentration, or Yoga, is the hindering of the modifications of the thinking principle.
In other words, the want of concentration of thought is due to the fact that the mind — here called "the thinking principle" — is subject to constant modifications by reason of its being diffused over a multiplicity of subjects. So "concentration" is equivalent to the correction of a tendency to diffuseness, and to the obtaining of what the Hindus call "one-pointedness," or the power to apply the mind, at any moment, to the consideration of a single point of thought, to the exclusion of all else... Upon this Aphorism the method of the system hinges. The reason for the absence of concentration at any time is, that the mind is modified by every subject and object that comes before it; it is, as it were, transformed into that subject or object. The mind, therefore, is not the supreme or highest power; it is only a function, an instrument with which the soul works... (Book I, Concentration)