Assalaam Alaikum Wa Rahmatullahi Wa Barakatuh,
I'll try to explain in the view of Risale-i Nur by Bediuzzaman Said Nursi.(Being content with what Allah has decreed for us) :
"When making a precious bejewelled and embroidered garment, a skilful craftsman employs a poor man in return for a commensurate wage. In order to display his skill and art, he dresses the poor man in the garment, then measures it and cuts it, and lengthens and shortens it, and making the man sit down and stand up, he gives it various forms. So does the wretched man have the right to say to the craftsman: “Why are you interfering with this garment which makes me beautiful, and altering and changing it? Why are you making me stand up and sit down, disturbing me and causing me trouble?”
In exactly the same way, in order to display the perfections of His art through the embroideries of His Names, the All-Glorious Maker takes the essential nature of every sort of being as a model, then He clothes them all and especially living creatures in the garment of a body be-jewelled with senses, and inscribes it with the pen of Divine Decree and Determining; thus demonstrating the manifestation of His Names. In addition, He gives to every being a perfection, a pleasure, an effulgence, in a way suitable to it and as a wage.
Has then anything the right to say to the All-Glorious Maker, Who manifests the meaning of, the Lord of All Dominion has free disposal over His realms as He wishes: “You are giving me trouble and disturbing me.”? Hasha ! (Allah forbid) In no way do beings have any rights before the Necessarily Existent One, nor can they claim them; their right is to carry out through offering thanks and praise, what is required by the degree of existence He has given them. For all the degrees of existence that are given are occurrences, and each requires a cause. Degrees which are not given are possibilities, and possibilities are non-existent as well as being infinite. As for instances of non-existence, they do not require a cause. For example, minerals cannot say: “Why weren’t we plants?”; they cannot complain. Their right, since they have received mineral existence, is to offer thanks to their Creator. And plants may not complain asking why they were not animals; their right is to offer thanks, since they have received life as well as existence. As for animals, they may not complain that they are not humans; the right over them rather, since they have been given the precious substance of spirit in addition to life and existence, is to offer thanks. And so on.
O complaining man! You did not remain non-existent; you were clothed in the bounty of existence. You tasted life; you did not remain inanimate, nor become an animal. You received the bounty of Islam; you did not remain in misguidance. You have experienced the bounties of good health and well-being!
O ungrateful one! Where did you win the right not to offer thanks in return for the degrees of existence which Almighty Allah has given you and are pure bounty. How is it that because exalted bounties which are contingencies and non-existent and which you do not deserve have not been given you, you complain about Almighty Allah with meaningless greed, ungrateful for the bounties you have received? If a man rises to an exalted degree like climbing to the top of a minaret and finds a high station, and on every step receives a large bounty, then does not thank the one who gave him the bounties and complainingly asks why he could not have risen higher than the minaret, how wrong he would be, what an ungrateful denial of the bounties, what great foolishness it would be; as even a lunatic would understand."
From:
http://www.lightofquran.info/24letter.htm