Can every sin, no matter how small, nullify all good deeds?

On the Day of Judgment, good deeds and evil deeds will be weighed. The weighing of good deeds will save their doer, while the weighing of evil deeds will place him under the will of Allah. Fear of one's deeds becoming nullified is good, but it should not turn into a pathological obsession that prevents one from performing acts of obedience. A Muslim must strive to learn what constitutes obedience and what constitutes disobedience, and not assume something is a sin when it is not. Not every disagreement with a parent is an act of disobedience. One must avoid sins and seek forgiveness for them, abandon pathological obsessions that are harmful and useless, and continue to strive against them.