NOTES for Eph 5:10-11
Paul repeatedly reminds the Ephesian Christians that the spiritual life of a Christian is incompatible with any conscious sin. Of course, through ignorance or weakness everyone sins in one way or another, and this will continue until human nature is fully transformed. But this gives a Christian no grounds for taking sin lightly, confident that "God will forgive everything" because "in Christ every sin is forgiven."
After the coming of Christ, a person is indeed never again left alone before God with his sin. He can always ask the Savior to intervene in the situation, and then his sin ceases to be only his own problem and also becomes Christ's problem, which He resolves together with the person, taking upon Himself the consequences that otherwise would have fallen on the sinner's own head.
But even with such intervention, the situation can be changed radically only when the person repents of his sin and renounces it, not when he considers himself entitled to go on sinning in the hope that "Christ will settle everything," appealing to the fact that sin is unavoidable until a person is fully transformed. Meanwhile, judging by the apostle's words, one can think that in the Ephesian church there were also people who treated sin rather lightly. Paul addresses mainly them, reminding them that Christ's help in freeing a person from the consequences of a committed sin does not in any way remove that person's responsibility for the sin itself. One cannot continue sinning as before, living in the customary pagan way of life, and count on being able, later, at the end of one's life, to repent of everything at once and then somehow have everything work itself out.
The point is not that on the last day of earthly life it is too late to repent, but that a person who was not afraid to sin throughout his entire life will very well be unable to repent on his last day on earth. Of course, a miracle is always possible, but it is hardly worth rejecting the path of righteousness and sinning in the hope of a miracle at the end of life. This is what Paul reminds those Ephesian brothers of his who either forgot what he had told them or never knew anything of the kind.