Emotions are basically the waves of feelings that arise in our mind. Due to these emotions our mind feels happy, distressed etc. There are many types of emotions that arise in our mind like love, hate, anger, jealousy, infatuation, fear, grief, compassion, happiness, distress, pain & pleasure etc. Out of these love, compassion, happiness, pleasure etc. are called positive emotions while hate, anger, fear, jealousy, infatuation, grief,distress, pain etc. are called negative emotions.
Emotions are required in our life as without these, one's life is mere mechanical. The difference between a robot & human being is that humans have emotions, feelings while a robot is not having that. Both robot & human being have intelligence but only humans have emotions, feelings etc. in their mind. Emotions make life pleasant, enjoyable unless until these are sensible and within limits. But when emotions are uncontrollable & beyond limits then mental equilibrium of a person is disturbed. Also negative emotions like hate, anger, jealousy, infatuation, grief, etc. destroy one's mental & physical health.
Bhagwat Gita is a great book which teaches us how to control our emotions & how to remain equipoise, calm when such emotions empower our mind. In ancient times "Arjuna" was involved in a war against his enemies (some of them his own relatives too) but he refused to do his duty of fighting a righteous battle as he got infatuated with emotions & started thinking of his enemies as his own near & dear ones. He told his master "Lord Sri Krishna" that he is going away from the war & do not want to fight on the battle field. Arjuna's mental equilibrium became disturbed due to negative emotions & he got deeply depressed. To overcome his disciple Arjuna's depression & to motivate him to fight a righteous war, "Lord Sri Krishna" gave the great teachings of "Bhagwat Gita" to his disciple "Arjuna". After listening to all these great teachings, Arjuna's mental health became well & he became motivated & energetic to fight the war.
As per Bhagwat Gita our true nature is that we are a "Soul" which is beyond mind. "Soul", our true self in this body of ours is a witness to everything while the drama of life with all the emotions in our mind goes on. "Soul" is only a witness & does not take part in this drama of life. All the emotions whether these are positive or negative arise in human mind only & we feel pain, pleasure etc. "Soul" is different from the mind but when we associate our true Soul nature with this mind, we also feel the qualities & emotions of this mind. The real tatva, the "Soul" is Satva & has no body, no mind, no intellect, no ahamkara (ego), no memory & no senses. "Soul" is beyond the body, the senses, the pranas and the four-fold interior substance consisting of the mind, intellect, ego and memory. Emotions are product of Maya; these are simply illusory, transient things & we should not associate our true self ("Soul") with these. We should know ourself to be that "Soul" who is beyond the unreal & should not be affected by the qualities of nature (Maya) which affect our mind.
Below are few verses of Bhagwat Gita which describe the above said:
"na-asato vidyate bhavo
nabhavo vidyate satah
ubhayor api drsto ’ntas
tv anayos tattva-darshibhih" (Bhagwat Gita: Chapter Two verse 16)
"Sri Krishna said: Arjuna, the unreal has no existence, and the real (soul) never ceases to be; the reality of both has thus been perceived by the seers of the truth."
tams titiksasva bharata" (Bhagwat Gita: Chapter Two verse 14)
"Sri Krishna said: O Arjuna, the contact between the senses & their objects, which give rise to the feelings of heat & cold, happiness and distress, etc. are transitory & fleeting in nature, therefore Arjuna, one should not get swayed by these and one must learn to tolerate them without being disturbed by them."
"yam hi na vyathayanty ete
so ’mrtatvaya kalpate" (Bhagwat Gita: Chapter Two verse 15)
"Sri Krishna said: Arjuna, the wise human being to whom pain & pleasure, happiness and distress etc. are alike, and who is not tormented by these contacts i.e. remains steady in both is certainly eligible for liberation & immortality."
So we should not let our mind be swayed with these emotions in our life & in the midst of these emotions we should be rational. It is only when we are carried away with these emotions that we harm ourself or others with anger etc. So let's know our Soul nature which is beyond these emotions. Let's always establish ourself in the Soul nature so that our mind is not swayed with these emotions & is always calm, composed & peaceful.
Jai Shri Krishna