Why are people not allowed to partake of the sacrament for periods of time?  I have a friend who sinned and talked to the bishop; then she wasn't allowed to partake of the sacrament for a while.  But, if she was in the process of repenting, wouldn't that obviously show that she was desirous of keeping the commandments-as it is mentioned in the blessing of the bread?  I understand that it is a sacred ordinance and you are not supposed to partake of it if you are not worthy, but doesn't the whole repentance process mean anything?

The bishop is the president of the Aaronic Priesthood in a ward, and unless a member of the stake presidency is in attendance, the bishop presides over the administration of the sacrament. In his role as a judge in Israel, the bishop has the keys of discernment and can, if so inspired, withhold sacrament privileges from a member of his ward as part of the repentance process.

The idea is to give an individual, (depending on the specific circumstances of the case) sufficient time to complete the repentance process. This process includes abandonment of the sin, and depending on the specific sin the bishop may impose a "probationary period" in which the penitent member will prove his/her readiness for the sacrament and other membership privileges.

Such "probationary period" is one of the elements in the Church disciplinary system, and is used with care, never as a form of retaliation or harassment. It is only imposed upon a member when a bishop feels by the Spirit that this would be in the best interest of a member's full repentance and consequent spiritual advancement.