Mascharya is a feeling of jealousy when someone else gets ahead of us. It is a state of intolerance born by seeing good qualities in others. It is a strong emotion that can break any strong relationship. A feeling of unhappiness and anger because some one has something which you cannot possess or someone that you want. It is all about not accepting good qualities in others and is one of the six bad vices. Mascharya(jealousy ) is a form of hatred built upon insecurity and is classified as a mental disease.
God does not like people having jealousy in their minds. Arjuna became dearer to Lord Srikrishna, as the former is devoid of Mascharya(jealousy).
In Bhagavat Gjitha Chapter 9 Verse 1, Lord Srikrishna says to Arjuna as follows:
idam tu te guhyatamam pravakshyamy anasuyave
Jnanam vijana sahitam yat jnatva mokshyase shubhat
Because you are not jealous I shall now explain to you the greatest of all secrets. I shall explain this knowledge and it's realization knowing which you will be released from all miseries of material existance.
There is a story in Bhagavath Purana, that how Rishi Narada get rid of his jealousy. It runs like this in brief:-
GandharvaThumbura and Rishi Narada are both musicians and great devoties of Lord Vishnu. Once they both went to Vaikunta where Thumbura sang a melodious song in praise of Lord Vishnu and Goddess Lakshmi.
Pleased with his song, Lord Vishnu presented him many divine jewels and clothes. Narada became jealous of Thumbura. He decided to please Lord Shiva and learn music from Him and became the best Musician than Thumbura. Lord Shiva pleased with Narada's request and taught him Music. But Lord Vishnu and Lakshmi still did not feel impressed with his music to give gifts.
Narada then practiced music several years with the hope that he would become the best singer than Thumbura. But even that was not sufficient. Finally Narada decided to give up his jealousy and hatred towards Thumbura. Therefore he approached Thumbura and requested him to teach music. Thumbura agreed and taught Narada all that he knew. Therefore Narada went to Dwaraka and sang a song for Lord Krishna, who said " now your music is wonderful because it is not tainted with jealousy ". Saying that Krishna then offered him some divine gifts in appreciation.
In Mahabarath, Bishma Pitamah says that the person who is not jealous of the wealth of others and is not attached to luxuries of life is indeed a saint, and will always overcome his life's adversities.
We must understand that the laws of nature that operate to give us results of our karma (actions) are just and unbiased. Jealousy prevents receiving devine knowledge from great people. So as long as this quality is annihilated the higher knowledge cannot be in our reach. One must be free of jealous towards others, which shortens one's life span. We must understand that if any person is becoming successful then he must have done something good in this life or in his previous births.
When we acknowledge that everything comes from God who is completely just, then we start treating the success of others as His grace. .