Rebirth does not take place without cause.
The causes of birth in the six realms are the six afflicting emotions: (1) arrogance, (2) jealousy, (3) desire, (4) ignorance, (5) greed, and (6) hatred.
These afflicting emotions in turn are rooted in the dualistic concepts of the mind. Dualistic concepts arise as soon as our mind grasps at the “self” of any mental object, perceiving mental objects as truly existing entities.
Having tightly grasped at the “self,” we form the habit of differentiating between this and that, instead of perceiving oneness.
This habit of discrimination arouses the afflicting emotions of liking and disliking, wanting and not wanting, attachment and hatred. Then we put those emotions into vocal and physical expression.
Repeated patterns of positive mental and physical actions cause happiness and result in rebirth in high realms and in pure lands.
Negative mental and physical actions cause sufferings and result in rebirths in the lower realms.
If you are a highly accomplished master, you may attain liberation from the cycle of rebirth by becoming enlightened.
When you perfect the realisation of the wisdom of openness—the basic emptiness that is our nature—then your concept of grasping at “self” will be liberated, marking the end of suffering and karmic causation, which means that no more rebirths will occur.
With the attainment of this realisation, you can become the source of effortless benefits for many others.
Source: Taken from the following book — Thondup, Tulku. Peaceful Death, Joyful Rebirth: A Tibetan Buddhist Guidebook. Boston, MA: Shambhala Publications, 2005.
Repeated patterns of positive mental and physical actions cause happiness and result in rebirth in high realms and in pure lands.
Negative mental and physical actions cause sufferings and result in rebirths in the lower realms.
(Tulku Thondup, Peaceful Death, Joyful Rebirth)