I can understand Hosea saying to God's children, "It is time to seek the Lord; but for David to say to God, "It is time for thee, LORD, to work...," that can be frightening. One would of necessity have to have heavenly approval for such seeming brashness. Without such authority it would be presumption at its very worst.
But, thank God, we need not fear and tremble in approaching His throne with such boldness. Our great God has condescended to His human creation making such statements as: "Command ye me"; "Ye that make mention of the LORD, keep not silence, And give him no rest, till he establish..."; "Put me in remembrance: let us plead together: declare thou..." These, and many other like scriptures, give divine credence to such seemingly nervy praying.
David's prayer was not one of impatience, he knew how to wait on the Lord, but rather one of imminence. In his current circumstances, the situation had become out of hand. Truly, it was literally out of his control. Therefore, it was obvious it was time for divine intervention. Thus, "It is time for thee, Lord, to work." Whenever the natural has exhausted all its means, it is then the supernatural is to be called upon. God invites us, "Come now, and let us reason together, saith the Lord." God okays us to sit down and reason with Him. As Job said, "Order [your] cause before him, and fill [your] mouth with arguments."