The true believers must supplicate to Allah that He makes them firm and resolute on the wilayah of the Imam and that they can move spiritually closer to the Imam. They must also make du’a that the blessing and approval of the Imam (over his true followers) is not removed from a person and that one does not lose this great spiritual rank once he has attained it!
For example, if a person is blessed to be among the companions, helpers and Shi’a of the Imam (either during the period of the occultation or during his advent), then this blessing which has been bestowed upon him should be protected and there should be no change in his status (of closeness to the Imam) nor should he do anything to have someone else put in his place. In actuality, this is the same thing which we recite in the following du’a:
وَ لاَ تَسْتَبْدِلْ بِنَا غَيْرَنَا فَإِنَّ اسْتِبْدَالَكَ بِنَا غَيْرَنَا عَلَيْكَ يَسِيرٌ وَ هُوَ عَلَيْنَا كَبِيرٌ
“And do not place someone else in our place since surely Your replacement of us with others is something easy for You to perform, however this is something grave (and difficult) for us (to bear).”1