Any movement toward freedom and life, any movement toward God or others, will be opposed. Marriage, friendship, beauty, rest—the thief wants it all. So, it becomes the devil's business to keep the Christian's spirit imprisoned. He knows that the believing and justified Christian has been raised up out of the grave of his sins and trespasses. From that point on, Satan works that much harder to keep us bound and gagged, actually imprisoned in our own grave clothes. He knows that if we continue in this kind of bondage ... we are not much better off than when we were spiritually dead. (A.W. Tozer)
Sadly, many of these accusations will actually be spoken by Christians. Having dismissed a warfare worldview, they do not know who is stirring them to say certain things. "Satan rose up against Israel and incited David to take a census of Israel" (1 Chron. 21:1). The Enemy used David, who apparently wasn't watching for it, to do his evil. He tried to use Peter too. "From that time on Jesus began to explain to his disciples that he must go to Jerusalem and suffer many things . . . Peter took him aside and began to rebuke him. 'Never, Lord!' he said. 'This shall never happen to you!' Jesus turned and said to Peter, 'Get behind me, Satan!'" (Matt. 16:21-23). Heads up—these words will come from anywhere. Be careful what or who you are agreeing with.
When we make those agreements with the demonic forces suggesting things to us, we come under their influence. It becomes a kind of permission we give the Enemy, sort of like a contract.
Some foul spirit whispers, I'm such a stupid idiot, and they agree with it; then they spend months and years trying to sort through feelings of insignificance. They'd end their agony if they'd treat it for the warfare it is, break the agreement they've made, and send the Enemy packing.