Psa 69:17 Do not hide your face from your servant; answer me quickly, for I am in trouble.
18 Come near and rescue me; redeem me because of my foes.

In this world we divide the troubles we face.  We say there are troubles that come upon us that we do not deserve but there are also troubles we deserve.  It was because of something we failed to do. And so we we conclude that there are troubles that we must pay the price.
But in the bible we find that our troubles are measured by life and death standards. Why do we divide our troubles? Why does the world tell us we made our bed and now must lay in it? Because the world is a place where we award good behavior and punish the bad.  But the Psalmist teaches us that God measures life by redemption. You see history is  not really measured by the world's scheme.

The Psalmist never divides good and bad. Instead he reverses the bad by speaking the axioms. He uses the bad to argue for his weakness. How can God reward a sinner ? Because Christ death did not make it possible for sinners to do something to pay for their sins. Christ death sealed the curse on some people and obtained salvation for God's chosen. If there is any hope of being delivered in this world the curse of the law must be applied to all those who will curse God.
Our only hope is to die with Christ and be raised with Him to walk in continue deliverance. You see we who are delivered are always being saved by dieing. We are always speaking the curse of the law because we have failed to keep it.
If we think we have obeyed God's law then we deserve to be treated better or according to our efforts. God will accept our prayers because we are law keepers. But since Christ suffered the wrath of His Father how can we claim that we deserve to be accepted? We are saying that our works make God obligated to treat us like Christ. This is worse than the most vile sin.
So God had to curse anyone who comes on his own obedience. The least sinner and the worse sinner are made equal because everyone must die first in order to be acceptable to God . So we wish the curses on those who come without dieing.