You can prepare your next life in this life. Just like they are attempting to go to the moon planet, but the fact is they could not go there. Why they could not go there? The reason is that wherever you go, you must be fit for that place. Even in this planet, suppose somebody goes from one place to another place, he has to make himself fit to go there. He must know what is the temperature there. Accordingly, he'll take his dress. Then he'll have to take permission of the state, visa, passport. So many things you have to arrange, then you can go. Not that all of a sudden anyone can come to your country, Mexico, without arrangement. Similarly, if you want to go to the higher planetary system, then you have to make your arrangement in this life. You cannot go to the moon planet by force because you have got a teeny airplane. That is not possible. Therefore Bhagavad-gītā says, yānti deva-vratā devān (BG 9.25). A man can go to the higher planetary system when he is preparing himself to go there.
So there are millions and trillions of planets. Wherever you want, you can go. The descriptions are there in the śāstra. But there is another description, the kingdom of God. That kingdom of God is there beyond this material sky. So we have to take information where that spiritual world is there. You can have it from Vedic literature. In the Bhagavad-gītā it is said, paras tasmāt tu bhāvo 'nyo 'vyakto 'vyaktāt sanātanaḥ (BG 8.20). There is another nature, the spiritual nature, which is beyond this material nature. That material nature . . . Vyaktāvyakta means some portion is manifested and some portion is not manifested. And we get information from Bhagavad-gītā that the spiritual nature is beyond this manifested and nonmanifested cosmic situation. So Kṛṣṇa says, the supreme authority says, mad-yājino 'pi yānti mām (BG 9.25). If somebody cultivates Kṛṣṇa consciousness, he can go there. It is not difficult; simply you have to change your mode of life.
To become Kṛṣṇa conscious means to be pure in the original spiritual existence. We are pure as Brahman, as spirit soul, but because we have contaminated these material modes of nature, our consciousness is now different. So on account of different consciousness, there are three classes of men. One class of men is very intelligent; one class of men, very passionate; and one class of men, fools and rascals. So in order to understand your promotion to the spiritual world, you have to become first-class man. First-class man means brāhmaṇa. A brāhmaṇa means he is truthful, he is self-controlled, he is simple, he is tolerant . . . in this way there are nine qualification to become first-class man. And to become first-class man, the preliminary qualification is that you should not become sinful.
So instead of becoming sinful, to become pious, you simply follow these four regulative principles. The first principle is illicit sex. That is forbidden. Sex is not forbidden, but illicit sex is forbidden. That is not very difficult. Everyone wants. That is the necessity of the body, that sex. As we want to eat, as we want to sleep, similarly, there is sex desire. But if you want to become first-class man, then don't have illicit sex. Except marriage, do not have sex. The human society . . . therefore, human society, there is marriage. There is no marriage in the dog society. So therefore, sex life within marriage and regulative principle, that is not prohibited. That means anyone who follows these rules and regulation, he becomes purified and pious. Without becoming purified and pious, you cannot understand God.