Concerning the power to work miracles
Pope St Gregory the Great, writing in a letter to St Augustine of Canterbury,
as recorded by St Bede the Venerable in the Ecclesiastical History of the English People
"Finally, dearest brother, in all your outward actions, which by God's help you perform, always strictly examine your inner dispositions. Clearly understand your own character and how much grace is in this nation for whose conversion God has given you the power to work miracles. And if you remember that you have ever offended our Creator by word or action, let the memory of your sin crush any temptation to pride that may arise in your hear, and bear in mind that whatever powers to perform miracles you have received or shall receive from God are entrusted to you solely for the salvation of your people."
Gregory reminded Augustine not to boast of his achievements, noting that when the Apostles returned to Christ saying "Lord, even the devils are subject unto us, through thy Name" Jesus chided them "In this rejoice not, but rather rejoice because your names are written in Heaven". Don't lose sight of the eternal even for good things in the temporal.
In our own age, so-called 'celebrity pastors' and those who are devoted to them would do well to heed the words of St Gregory, who signed the letter above quoted, and all of his letters "Gregory, servant of the servants of God."
Bede's Ecclesiastical History can be found here and here.