An excerpt that is amazingly helpful to me and hopefully will be for you too:
"the sinner's inability to obey God does not nullify his duty to do so. This is a crucial point—perhaps the most crucial point of all—because it is the very point that ultimately distinguishes true Calvinism from both Arminianism and hyper-Calvinism. Both Arminians and hyper-Calvinists will protest that it is illogical or unjust to teach that God demands what sin renders us incapable of doing.
But it is neither illogical or unjust. Sin itself is a moral issue, and since sin is the cause of our inability, it is, as Jonathan Edwards said, a moral inability, not a natural one. The defect in man is his own fault, not God's. Therefore man's own inability is something he is guilty for, and that inability cannot therefore be seen as something that relieves the sinner of responsibility."
Excert from Phillip Johnson