A story from the epics
In the Ramayana, the monkey army reaches the sea while searching for Sita. Lanka is far across the water and nobody thinks they can jump that far. Hanuman sits quietly. Then wise old Jambavan reminds Hanuman who he is and how strong he is. Once Hanuman knows the truth about his own strength, he grows in confidence and leaps across the sea.
Hanuman always had the power. Knowing the truth is what let him use it.
Source: Valmiki Ramayana, end of Kishkindha Kanda (Jambavan speaks to Hanuman).
