Contentment
The Prophet of Islam once observed, “Successful is the one whom God has provided sustenance according to his needs, and he is satisfied with that provision.” (Sunan ibn Majah, Hadith No. 4138) It becomes clear from this observation that the secret of success lies in being content with what one has received instead of grieving over what one has not received. Whenever a person in the world tries to earn according to the right principles, he will earn enough to meet his needs. If he agrees to what he has earned, he will get the benefit in the form of peace of mind. But peace always comes from contentment, which means being satisfied with what one receives.
On the contrary, a person who underestimates what he has received and keeps running towards what he did not have will never be satisfied. For there is no limit to things in the world, no matter how many things a person accumulates, there will still be something that he will be tempted to acquire. In that way, he will always be greedy for more and more. Consequently, he will live a life of restlessness until the day he dies.