"Little children, let no man decieve you: he that does righteousness is righteous, even as He is righteous." -1 John 3:7
Again, that is John pointing out that believers are to be aware of some believers that think sin is no longer sin to live however he wants. Believers can know whom are abiding in Him from those that are not so as to not to follow after them.
If a believer sins, should he give up following Him then? No.
So what do we say when a believer quits because he has sinned? Tell him to ask Jesus to forgive him and ask Him to help him not to do that again.
Hebrews 12:1Wherefore seeing we also are compassed about with so great a cloud of witnesses, let us lay aside every weight, and the sin which doth so easily beset us, and let us run with patience the race that is set before us,[SUP]2 [/SUP]Looking unto Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame, and is set down at the right hand of the throne of God.
I believe the majority of responders agree with you in one point that a saved believer should not live in sin, but I believe you are glossing over scripture in that Book of 1 John if you believe a saved believer can never sin.
If you passed up doing a good deed, that is a sin.
James 4:[SUP]13 [/SUP]Go to now, ye that say, To day or to morrow we will go into such a city, and continue there a year, and buy and sell, and get gain:[SUP] 14 [/SUP]Whereas ye know not what shall be on the morrow. For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away.[SUP] 15 [/SUP]For that ye ought to say, If the Lord will, we shall live, and do this, or that.[SUP]16 [/SUP]But now ye rejoice in your boastings: all such rejoicing is evil.[SUP]17 [/SUP]Therefore to him that knoweth to do good, and doeth it not, to him it is sin.
His yoke is easy and His burden is light because all our hopes are on Him to help us not to sin and to follow Him, but not every saved believer are placing that kind of trust in Jesus Christ as their Good Shepherd to help them to do that.