The motivation for reading this teaching on the profound path of guru yoga should not be one of seeking only the happiness of this life; that is completely worldly dharma. That attitude is actually non-virtuous, so it is to be completely renounced. You should not even have the virtuous motivation of seeking the happiness of future lives, or even the virtuous motivation of seeking liberation. Not only is this teaching on the profound path of guru yoga a teaching on tantra, it is the highest level - maha-anuttara yoga tantra. This practice begins with a brief meditation on the dharmakaya, sambhogakaya and nirmanakaya and it ends with the maha-anuttara yoga tantra practice of the guru entering the heart. Therefore the only motivation for reading this should be the special motivation of bodhicitta.
Think: It is not sufficient that I myself be liberated from samsara, these aggregates caused by karma and delusion, contaminated by the seed of disturbing thoughts. I must achieve the state of omniscient mind for the sake of all the kind mother sentient beings who equal the infinite sky - on this body. The reason is that this body is qualified by eight freedoms and ten richnesses and that even in one day, even within one hour, even within one minute, even within one second, you can achieve any great purpose, any happiness for future lives, whatever you wish: the body of a human being or deva, any body, and wealth, perfect surroundings, helpers, anything. If you wish for liberation from samsara you can achieve it. If you wish for the peerless happiness of enlightenment you can achieve it with this body. With this body you can accomplish the causes for all those results.
Furthermore, it is not sure that you can create the cause by practicing dharma in other futures lives, because it is very difficult to create the cause of a perfect human rebirth. Therefore it will be difficult to find a rebirth such as this perfect human rebirth again. That is the main point. Even the perfect human rebirth that you have now will not last for a long time. Death can happen very easily; this life is so fragile, like a water-bubble. And the actual time of death is uncertain; it can happen even today, it can happen even while you are reading this book, right this moment.
To be able to take the essence of having this body by practicing the dharma right now on the basis of this body, to have the realization of bodhicitta, to achieve the state of omniscient mind, to be able to generate the whole path from contemplation of the perfect human rebirth up to enlightenment, depends on the very root: correct devotion to the virtuous friend. Therefore it depends on guru yoga practice.
Think: I must achieve the state of omniscient mind quickly and more quickly for the sake of all the kind mother sentient beings who in number equal the infinite sky, therefore I am going to read this commentary of the guru yoga practice related to Lama Tsongkhapa known as Ganden Lha Gyäma - The Hundred Devas of Tushita. In this way clarify the purest attitude, bodhicitta.