Prayer is for real. When we pray we are not indulging in wishful or contradictory thinking. We are not trying to squeeze something out of an unwilling deity. God gives willingly, yet it is good to pray hard in order to find out if we really want what we pray for. There are certain things that it is unreal or meaningless to pray for.
Abraham prayed and bargained hard but he knew when to stop. In fact he was asking God not to destroy the innocent with the guilty. Of course, if God let the guilty off or "converted" them, that would be wonderful! Abraham did not ask God to pardon the cold-bloodedly unrepentant since that would be a meaningless request.
In the Gospel Jesus assures us that when we pray we are knocking on an open door. God is a loving father, not a cranky (perhaps understandably so in the circumstances) head of a household. If He doesn't give what we want, He will give us what we need.
In the Our Father we first express the wish that we may so appreciate God's plans for the world that we will do all we can to forward those plans. In the process we may be surprised to find that we receive what we really need to make us happy.
Lord, I stand before You with open hands. You know what to put into them.