Necessity is out of compulsion to live, desire is out of competition.
As wind is the cause for waves in the ocean, desire is the cause for waves (disturbance) in the mind. The desireless mind is peaceful, calm and relaxed but desires (including unfulfilled past desires) disturb this calmness. Unfulfilled desires irritate and frustrate the mind and fulfilled desires generate new desires causing expectations, anxiety and worries. And out of new desires, only few get fulfilled and others remain unfulfilled and we get caught in this vicious cycle of fulfilled and unfulfilled desires.
However, everyone needs some basic amenities in life such as a house, money to buy food and clothing, a personal vehicle and bit of entertainment plus savings to take care of future exigencies. But the confusion is how to differentiate between desire and necessity and strike a balance between them.
Necessity is out of compulsion to live, desire is out of competition. Desire springs up from the ever-active unsatisfied senses and mental comparison with what others have and what we don’t have. Desire is never constant but ever increasing. Running behind desire is like that deer which runs after an illusory desert mirage wherein upon arriving at the identified spot it finds nothing and the mirage is visible further away at another spot.
There lived a rich man in a villa and in the opposite side lived a poor man in a hut. The rich man’s wife used to observe the peace at which the poor man and his wife lived but that peace she never felt neither in herself nor in her husband. Once when her guru (spiritual master) visited her house, she sought to know as to why is it that even though they eat rich and healthy food, yet they fall sick and the poor couple hardly ate anything yet remained healthy, they slept in air conditioned bedrooms yet got sleep with difficulty but the poor couple slept like logs of wood even in the hut, their future was well secured, yet they always lived in some unknown fear and the poor couple look fearless as if they are highly secured.
To answer the question, the master asked the rich lady to put some gold coins in a bag and ordered it to be kept quietly in the poor man’s hut in the night. Next day he left while saying that she should observe the poor man for the next two months. A couple of days later, she noticed that the poor man, who used to come back home early evening, had started coming back late in the night. Occasionally, she started hearing some quarrels between the poor man and his wife. She observed falling health and wrinkles of tension on the poor man’s face.
The rich man’s wife was amused at these developments as she thought that after getting gold coins the poor couple will look even more happier and healthier but the reverse of that had happened. Upon enquiry she came to know that the poor man after finding those gold coins in his house desired to add some more to them so as to secure his future, buy a house and other luxuries to enjoy. And towards this he started working double-shift, cutting down on his food and started consuming alcoholic drinks to overcome his stress. He also forced his wife to work and earn so as to save more money.
This changed attitude brought a lot of stress on the poor couple. They had no time for each other. They forgot what they had and started getting bothered for what others have and they don’t have.
They forgot to live in the present and started living in the future, thus losing the secured zone of contentment, losing their gratitude to God and getting entangled in illusory competition and eventually losing peace.
This is why it is often said by saints and scriptures, that desire is the main cause of mental disturbance!