Fear is an emotional trigger that every living creature is somehow rather too intimate or familiar with. It is a survival instinct that can be managed but only with regular practice.
Therefore, the moment you tend to feel fear especially the fear of public speaking, then remind yourself that you are in control. Slow, deep breathing is among the many effective ways of calming yourself down in the face of fear. You can also overcome fear by constantly reminding yourself that good things are found on the other side of fear.