Why can't we ask God for things based on our own deserving?

Les explains that Daniel's prayer in Daniel 9:18 is not based on Israel's righteousness or deserving, but on God's mercy. Daniel prays on behalf of his people and Jerusalem, the city called by God's name, saying they do not present their supplications for their righteousness, but because of His mercy. Les applies this to us today: we can never go before God and ask for anything because we deserve it; everything we get, every breath and heartbeat, is because of the grace of God. Even Daniel, under law and without the full knowledge of what we call the grace of God, nevertheless called upon the very grace of God. His prayer was a heartfelt cry, not just empty words, and it was directed to the same God we pray to today, though we are under a different economy. Les then points to Philippians chapter 4 to show the difference.