In most case, the bride would have much worries and she will constantly notice every little thing that goes wrong with her wedding. Her bridesmaid on the other hand, should know how to gently steer the bride away from her worries without agreeing with her worries so that she can emotionally help the bride.
Problems may occur and would even add to the stress of the bride when a bridesmaids also become worry and obsessed with the wedding herself. There may also be some instances where emergencies and accidents happen during the wedding and the bridesmaids started to make a scene about it instead of just keeping quiet about it for a while. A bridesmaid should know when to talk and when to make a scene since the wedding is not the time to make the bridesmaids the star no matter what happens evem she is wearing her bridesmaid jewelry gifts given by the bride..
However, there are still some side backs to not saying anything. For instance, a bride may not even know until the wedding is over why one of her bridesmaids was not able to attend her wedding until the wedding is done. A bridesmaid getting sick at the day of the wedding and because this bridesmaid does not want the bride to worry, she just simply relay the information of her not attending the wedding to the maid of honor or to the wedding planner.
A bridesmaid considering the bride's event and not her own welfare can guarantee that the wedding will go according to plan and without any interruption. Of course this rule does not only apply to bridesmaids, but to the whole wedding party including the parents of the bride and grooms them selves. However, there are some situations where the bride would want to know what is going on with those who are involved with the wedding, but for those brides who wish not to know, it is better to just keep their mouth shut and just say the information later after the whole wedding is done.