Don't be Sad
Do not challenge your Lord
By being contented, one is saved from being like those who challenge their Lord in His decrees and rulings. To understand this, one needs only look at the case of Iblees (the Devil). He argued and disputed with his Lord because he was displeased with His decree and ruling. Those who refuse to believe in Allah only do so because they seek to challenge Him in might and power instead of submitting to Him. Then they abandon His orders, perpetrate what is unlawful, and challenge His divine decree by showing resentment.