Some people practice the Dharma in the hopes of eliminating problems in their family, improving their health, overcoming difficulties in their careers etc. They pursue worldly things like fame and benefit. Then they may get some temporary benefit in this life, but it is not of the slightest use in future lives or the bardo. Your motivation is to benefit this life, therefore the fruition of your practice will also be used up in this life. Therefore, the motivation for Dharma practice is critical. When the motivation is faulty, no matter what practice you do, it becomes defective too.
I will tell you a real story about a practitioner in Xinlong, Tibet. There was a monk who recited the Mani mantra and Guru Rinpoche mantra several hundreds of millions times each. He gained great power as a result of his diligent practice. He could repel negative spirits such as those that caused illnesses in humans. With just a gaze, he could cause the illness to disappear from the sufferer’s body. Many people venerated him like a great Mahasiddha (great accomplished master). Due to his blessings, many of the problems and inauspiciousness in their families were resolved. Why? It was due to his vast accumulation of merits from the mantra recitation.
His fame spread more and more and many people came to him for help and blessings etc. Thus, he received many offerings and became a very rich man. As a monk, he did not have any descendants but his siblings had many children. When he was on the verge of dying, his nieces and nephews came to ply him with all kinds of nice words, but in reality they were just eyeing his possessions.
When this monk was in great suffering and near death, he had a pair of glasses that was made of crystal and very costly which he treasured very much. One nephew who was also a monk came and claimed, “My uncle loved me most amongst all his nephews. Therefore, this pair of spectacles is mine, “ and he snatched this pair of glasses away by force even before his uncle expired. In this way, one by one, all of this dying monk’s possessions were taken away from him even though he had yet to die. At last, when he finally died, he had a negative aspiration out of anger and vengefulness.
This monk did not have any kind of basic foundation and understanding of Dharma practice, but he simply plunged straight into reciting mantras as he knew it was meritorious. He did not understand what is virtue and non-virtue. He was ignorant of the teachings on Bodhichitta, the importance of motivation and the stages of visualization and meditation. Just like that, many people just recite the mantras like Mani mantra blindly, they do not understand anything except that reciting mantras has blessings, blessings for having a good family life etc. There is no proper motivation, they do not know the systematic path for practicing Dharma or what to visualize etc. Everything was done blindly.
This monk may be ordained, but he was practicing in a similar blind manner. Without any listening, contemplation and meditation, he just kept practicing diligently in a cave and in the end the result was some worldly benefits. So after his death he directly took rebirth as a demon. This was due to his merits after reciting so many mantras. Many great accomplished Lamas who tried to subdue him could not succeed as his merits from reciting so many mantras had not yet been exhausted. All the people who had taken his things or anyone who even merely touched them would die without exception. So you see, even though he was a monk and recited so many mantras, he took rebirth as a harmful spirit which belongs to the preta (hungry ghost) realm. When this birth as a demon finishes, his eventual rebirth will be in the hell realms due to the many beings he harmed as a spirit.
In a sense, this kind of ordained monk would be better off unordained, and all these mantras recited would be better off not recited. If he had not done these things, then perhaps he would not be creating such heinous deeds and this great result of suffering would not exist. In the same way… one must know the way to practice Dharma, recite mantras and create merits. If one did not know how to practice the Dharma well, it would be the case of inviting disaster to befall upon oneself.