An old saying says to make ourselves habitually consistent.
Then our lives can be like pictures, preserving the same representation they first received.
How can one be consistent who is inflamed by anger one minute,
and the next blazes up with fierce resentment?
Or what about one whose face burns at first, but, in an instant,
is changed to paleness – varying and changing its color every minute?
It is natural for one to be angry because generally there is good reason.
However, it is our duty to restrain anger.
We must not be carried away by fury like a lion, unable to settle down.
We must not spread tales or make family quarrels worse, for it is written,
“A wrathful man stirs up strife” (Prov 15:18).

One who is double-minded won’t be consistent.
Those who cannot restrain themselves when they are angry cannot be consistent.
David says it well, “Be angry, and do not sin” (Ps 4).

He does not condemn his anger, but indulges his natural tendency.
One cannot prevent these tendencies but can moderate them.
Therefore, even though we are angry,
we must only admit that 
our emotion is natural and must not sin.
St. Ambrose