Begin by reviewing v1-6. Then move on to today's verse.
7 That man should not think he will receive anything from the Lord; (NIV)
7 For that person must not suppose that he will receive anything from the Lord; (ESV)
If we doubt God, if we don't trust in His goodness, we dishonour Him and God will not answer our prayers for wisdom (or anything else). God is good. God is love. We can trust Him!
Repeat, repeat, repeat!
LeRoy Eims on the importance of Scripture memory: "I think two of the master strokes of the devil have been to convince people he doesn't exist, and that Scripture memory is only for children. He remembers the humility of defeat when Jesus Christ, who was tempted in all points like as we are, met him with the Word of God." (What Every Christian Should Know About Growing; p. 26-27)