If you tell someone they are stupid and insult them, different people will react differently. Some will take it personally and feel bad, others will get aggressive and reply in kind. However, if you give anyone love and positive emotions, everyone will react the same. There are always exceptions, but three headed twins are rare and to be treated with different rules.
If all beings have a heart and blood and other organs similar to its species, then it stands to reason that its inner ways must be consistent as well. This proves that positive emotions are of the nature of humans because they are consistent to all of us. Reactions to negative emotions are not consistent and therefore not natural or part of the created being in its original form.
Negative emotions and reactions are formed in the personality and mind, the individuals character. They are not part of the essence. If they are part of the personality, they must have been acquired after the personality was brought into existence, which could be anywhere from conception to a young age. The essence or soul existed far earlier than that, the point of its original creation. If we take it that our soul, or whatever it is that you believe continues, accumulates characteristics from life to life and these come with us to give a child a particular personality, then still we say that is acquired and not part of the original essence. The key is the return to the beginning, not just life to life.
The consistent reaction proves the similarity, the unity of all humans. The different reactions to negative emotions shows the separate individual differences that are not connected throughout the species. Therefore what is real is what is consistent to us all and what is not consistent is not permanent or real or part of our essential essence.
Let us assume that the word real means permanent, eternal, everlasting. What is real cannot change, what is not real is temporary, it comes and goes from life to life, and can be changed.
If a person is seeking their true nature, they must look towards what is real and what is not. In understanding we can begin this work. Without understanding, then intellectual information is virtually useless in achieving the final goal.
As the accumulation of anything requires the elimination of its loss, so too in achieving spiritual growth. We require the energy necessary for that, which is positive energy and thoughts. Let us take a different view of negative thoughts. Negative thoughts are not a thing in themselves, but rather they are holes and leaks in the vast storehouse of positive energy. The more negative thoughts or emotions, the more holes and leaks, and the more difficult it is to accumulate the necessary critical mass of positive focused energy necessary for an experience of spiritual reality or self perception.
Meditation and other such practices are said to be methods of building up and acquiring spiritual energy. Internal martial arts and Yoga say the same thing, through the exercises of Hatha Yoga and Qi Gong, breathing and other practices, one acquires more personal power and energy which can be directed and used as one desires, it also provides opportunities for experiences of wisdom.
This again proves that negative emotions are not part of our true essential nature. How could that which puts holes in that which is created to store be a natural part of its creation. If this were so, then the creator is flawed. You can decide what you want to believe.