Knowing and accepting your own fallibility is one of the first steps in living at peace with yourself. Knowing and accepting the fallibility of others is a further step to living at peace with them.
By accepting this fallibility state, when failure happens it will not come as a surprise. Never gloat over the failure of others, the fallen state is common to us all.
Human failure is an inevitability for all so be gracious and forgiving when it happens.