This is a fundamental question and many of the world's mighty brains have searched for its answer.
We know that this universe is full of chemicals - both artificial and natural. We know how these natural chemicals like oil and gas are formed in the earth's crust. We know chemical composition of the sun. We also know how our earth and other planets have formed. We know the chemistry behind many other phenomenon.
What we do not know is who initiated these vital chemical reactions? Who defined their rules? Who created the basic elements? ....... ? ....... ? Here we come to the conclusion that this universe is created by a super power - The God.
The sages in Upanishads (a sacred Hindu scripture) have named this super power as the "Brahman". According to these sages, "Brahman" is the cause behind the existence of this universe. A portion of this "Brahman" is existing within everything in the universe. That is why everyone should be treated equally. Suicide is an attempt of destroying a portion of this cosmic power and hence it is an extreme offence.
We should nurture this source of energy by following a healthy organic lifestyle rather than destroying it by consuming unhealthy fast food and following a sedentary lifestyle.