The Ways of Ascent - 70:19 Indeed man is of an anxious nature.
In the context of verses 19, 20, 21; those who conditionally worship/serve Allah:
Prophet Hud/11:9 If We give man a taste of mercy from Ourselves and then take it away from him, he becomes despondent and ungrateful.

The Night Journey/17:83 When We bestow a blessing on man, he turns away and turns aside. And when evil touches him, he falls into despair

The Pilgrimage/22:11 Among mankind there are some who serve Allah conditionally. He rejoices when his affairs go well, but when trouble befalls him, he turns away. Thus he loses the world and the Hereafter. That is the real loss.

Explained in Detail/41:49 Man never tires of asking for good. But when an evil touches him, he is despairing, pessimistic.
Explained in Detail/41:50 "When We give him a taste of mercy from Us after his distress, he says: "This belongs to me. I do not think that the end of the world will come. And if I am returned to my Lord, there are better things for me in His Presence."We will certainly inform the disbelievers of the true nature of what they used to do. We will make them taste a severe torment."
Explained in Detail/41:51 When We bestow a blessing on man, he turns away. And when an evil befalls him, he begs and pleads.

Council/42:48 If they turn away, We have not sent you to them as a guardian; your duty is only to inform. When We give man a taste of mercy from Us, he rejoices in it; but when evil befalls them as a result of what they themselves have done, then man becomes ungrateful.

The Ways of Ascent/70:19 Indeed man is of an anxious nature.
The Ways of Ascent/70:21 And when good touches him, he is stingy.

The Romans/30:48 Allah sends the winds to drive the clouds, and He spreads them in the sky as He wills, and you see the rain coming out of them. When He sends it down on whom He wills of His servants, they rejoice.
The Romans/30:49 But they were despairing before it rained on them.
The Romans/30:50 Look at the fruits of Allah´s mercy; how He revives the earth after its death. Just like that He will raise the dead. He is all-powerful.
The Romans/30:51 But if He sends a storm and they see (the crops wither and turn yellow), they immediately begin to disbelieve and be ungrateful.

Council/42:28 He is the One Who sends down the rain and spreads His mercy after they had given up hope. He is a Friend Worthy of Praise.