Do not look at the worldly wealth which We have given enjoyment to [certain] categories of the disbelievers, nor grieve over (this destruction of) them and be kind and gentle to the believers,
Meaning:-
Grieve: to feel pain or sadness as a result of a loss, or to cause pain or stress to someone.
destruction: damage so bad, the action or process of causing so much damage to something that it no longer exists or cannot be repaired.