Envy is the biggest cause of mankind's downfall throughout history. When one nurtures discontentment, that feeling will eventually lead to hatred and jealousy to those perceived to be better then they are – whether in accomplishment, beauty, status, riches or even number of children. It is the worst characteristic to have, because this emotion can breed other diseases of the heart, which we will come to later, insha Allah.
It was the envy that Iblis harboured for Adam AS that clouded his judgment, and caused his own downfall. Iblis was so consumed with envy for Adam's AS higher status, that he was bent on destroying Adam AS, even if it meant destroying himself in the process.
We also see how envy caused the first murder in mankind, when one child of Adam AS, Qabeel, killed his own brother, Habeel.
Envy is only justified in the following circumstances:
(1) a man whom Allah has given knowledge of the Qur'an, and so he recites it during the night and during the day; and (2) a man whom Allah has given wealth and so he spends from it during the night and during the day. [Bukhari & Muslim].
In all other cases, envy is prohibited.
Envious people are easily recognizable – they are habitually comparing themselves to other people, constantly wishing that they were in the shoes of others and are secretly or openly harbouring ill will for those more successful than they are – whether in their personal lives, monetary terms, and even in closeness to Allah!
The envious always measure themselves by what others own or achieve. An envious person lacks focus, because instead of chasing his own dreams and establishing his own goals, he pursues what others have, only to find out, repeatedly, that this does not bring happiness. Think of the people who upgrade their cars, change their furniture, buy a new bag or electronic item, where their only motivation was envy for what another had!
Envy is like a cancer, and if left untreated, can spread and destroy a person's soul in a very short time.
A truly happy person never feels the need to compare, because he has learnt to be happy with what he has. Envious persons, on the other hand, are often insecure, which is why they benchmark their happiness and successes against what others have.
The root of this is again, lack of contentment, which denotes a much larger problem, being the lack of respect for what Allah chosen to give him and those around him. This state of mind makes the envier vulnerable to the persuasions of Iblis, who fuels the envy even more and sucks him into a deeper state of misery.
In most cases, the envy is not even justified! Also, in many cases, envious people simply feel a sense of entitlement even if they did not lift a finger to attempt any sort of achievement, without acknowledging the effort and sacrifices that others had put in to achieve what they had. For example, being envious of a friend's happy marriage without considering all the sacrifices, compromises and contributions that went into making the marriage a success.
In the story of Habeel and Qabeel, Habeel offered the best of his sheep to Allah, whereas Qabeel offered the worst of his crops - and then got angry and envious that Habeel's sacrifice was accepted whilst his was rejected!
Envy is one of the key characteristics of Iblis and is extremely toxic. It does nothing but poison the mind and heart. Just like Iblis, an envious person is ungrateful to Allah, and does not have any respect for the wisdom and qadr of Allah, which means that even his pillars of faith in Islam are corrupted.
There is no such thing as a happy and envious person - these two emotions are mutually exclusive. For one to exist, the other has to be destroyed. For you to be happy in this world and the next, the envy has to go.
Return to the fundamental principles of Islam. Focus on yourself, not on others, and always be grateful to Allah. Never compare or yearn for the lives of others. Trust in Allah's wisdom – He gives some and deprives some, for a reason that only He knows. Be grateful for what He has allocated you, and ignore what He has allocated others.
Remember, Allah is fair, and despite any imbalances you may see from your own limited understanding, life is fair. You just don't realize it because you're viewing things from one angle only.
The less you compare with what other people have, the easier your life will be. Remember that Allah will question you for what you have, not for what others have!
The day you are thankful for what Allah has allocated for you and you free yourself from envy, will be the day you truly experience happiness.