How sound is the attribution of this saying to God: "O My servant, you wish and I wish, and naught occurs except what I wish. If you submit to Me in what I wish, I will suffice you in what you wish"?

The narration has not been transmitted with a sound chain of authority, but Al-Ghazali mentioned it in "Ihya' Ulum al-Din" using a صيغة التمريض (a form indicating weakness of transmission): "And it is narrated that Allah Almighty revealed to David, peace be upon him: 'O David, you desire, and I desire, but only what I desire comes to pass. If you submit to what I desire, I will suffice you concerning what you desire. But if you do not submit to what I desire, I will exhaust you in pursuing what you desire, and then only what I desire will come to pass.'" Likewise, Al-Hakim Al-Tirmidhi mentioned it in "Nawadir al-Usul." It is well-known that everything that occurs in the universe is by the will and desire of Allah.