Before I can answer that, you will have to answer me how can I do anything God did not "ordain" me to do. If He "ordained" me to choose against Him, where is my fault?
Just to be certain, of course I was referring to the ubiquitous "you", not you personally. I am talking in terms of salvation. -- Since I believe that God ordains "everything", I would have to say that none of us can do anything God did not ordain. When someone "chooses" against Him, I really don't look at it in terms of fault, I look at it in terms of responsibility.
A loose comparison might be that an executive is ultimately responsible for the actions of his subordinates, but he might not be at all to "blame" for a particular mistake made by one of them. Since God has no duty to us either in salvation or in any terms of the human concept of "fairness", we are still responsible for our sin.
My dear friend, I think part of the reason we don't understand each other is because you seem to make up meanings of words. The sentence above is a circular argument, because fault is synonymous with responsibility, i.e. fault: "responsibility for a mistake or an offense; culpability" (dictionary.com), or "responsibility for wrongdoing or failure [the accident was the driver's fault]" [Merriam-Webster's].
If all we do is what God "ordained" us to do, then we bear no fault for anything we do. Whether we sin or not is God's will, and not ours, so no matter what we do is part of God's plan, and ours is simply to carry out the task He assigned us to do.
A loose comparison might be that an executive is ultimately responsible for the actions of his subordinates, but he might not be at all to "blame" for a particular mistake made by one of them
Whether we do good or evil, it is through obedience to God's will in your theology. If we make a "mistake" it cannot be against His will and if it isn't against His will, then it is not our fault. Judas was "ordained" to "betray" Christ so that, in Calvinist theology, the choreography plays itself out, and all the actors on the stage were simply doing their assigned part.