The Buddha told us that it's better to get out of reincarnation as soon as possible as it's very dangerous to be in reincarnation. According to the Buddha, human does not always reborn into human. There are several realms in which one can be reborn. Some of them are good and some of them are bad paths. People can be reborn in heaven, hell, animals or hungry ghosts path. If a being is very mean and does not like to give to the needy, then they will go to the hungry ghost path after death. If a being did many bad things, they would go to the hell or the animal path.
According to the Buddha, heaven is still in the path of incarnation. Beings can go to the heaven by doing many good things but once their merits used up, they will go to another path like the animal path or other bad path. In heaven, it is only for sense pleasure. That explains why it is dangerous to be in the incarnation because we do not know what path we are going to go after being a human. For example, a human can become a being in the heaven but once his/her merits used up, he/she will become an animal, then when the his/her karma are ready, he/she will become a human again, then if this being do bad things in this life, then he/she will go to hell. That explains why it's better to get out of reincarnation, as it's much easier to do bad things than do good things. Also, only human can have the opportunity to do good things, as beings in the hell, animal and hungry ghosts path are either too painful or does not have the wisdom to do good things. Once a human being fall into the bad paths, it would be difficult to get out from it. In general, we create bad karma by mind, speech and action. The most common way for modern people to create bad karma is eating meat and use materials like foam which damage the environment. That's why it's better to become a vegetarian and use less harmful materials. According to a senior monk, if over70% of our karma is good, we would be able to keep our human body.
The Buddha told us that any beings can become a Buddha, the difference between other beings and the Buddha are the level of craving, aversion and ignorant (the higher the level, the worst path beings would go to). If beings do not have these negative qualities, they would attain enlightenment and does not need to reincarnate again (no birth, aging, birth and death). That's why the Buddha thinks all beings are equal. In other words, all beings originally have the same qualities as Buddha, their mind have covered by the negative qualities and the Buddha have taught us methods to remove them, so that they can attain enlightenment and Buddhahood.
I will discuss different methods that are suitable for modern people to practice Buddhism later.
