The Rabbis try to encourage us to be careful with חמץ on Pesach. They say that one who takes such care, will be guaranteed a שנה טובה.
This explains the difficulty in deciding which חמץ one should dispose and which he should sell. One needs to be honest with what he can afford to throw out, and what he cannot.
This idea also applies to חמץ שעבר עליו הפסח. If one did not dispose of the חמץ and did not sell it, it is forbidden to have any benefit from it. This also requires honesty and fear of Heaven to do the right thing.
We should be careful to ask local store owners to produce a certificate showing that they sold their חמץ. This certificate titled, אישור מכירת חמץ should already be seen in stores today.
Among other things, Pesach is a holiday that requires a great deal of fear of Heaven.