The infused virtues and the gifts of the Holy Spirit are absolutely indispensable to man for his being able to act supernaturally. The infused virtues dispose and prepare him for action; they make him able to act, but, without the gifts – without the supernatural assistance – he will not be able to pass from the capability to act to an actual act.
The gifts of the Holy Spirit are the sails, which enable the boat to receive the divine impulse of the Holy Spirit and move to the open sea, and eventually to reach the port of destination. But those sails must be properly set and unfurled, otherwise the boat will not be able to go forward.