Fear is a strong aversion so is a form of vedana and therefore samudaya.In principle, therefore, it can be a doorway into a deepening of life.
One can be overcome by it - i.e. lose control.We are human. To expect that one will always and all the time be master of one's soul is hubris.
One may have to give in to it for a time. However, everything changes and one may be, in varying degrees, changed by the process.
Sometimes an attack of fear can be a purification, it puts things into perspective. Defeat can breed humility. Proximity to a fatal encounter can make ordinary worries seem trivial.
Fear may lead to flight, to freezing or to hiding. These are survival tactics deeply inbred into us. When encountering a big bear in the forest, or an enemy with a knife, they may be quite appropriate.
It is also common for us to psychologically run away, freeze or hide in response to imagined threats to our ego, the ego being the psychological avatar with which we attempt to play the game of life. Thus we may build up strategies of life based upon pure fantasy.
Social life is full of such fantasies which is why Buddha talks about ekagata - living as if alone. Lao Tse's principle of returning to one is the same idea.