"The start of the conquest is to conceal anger, to allow it no way outBut once we allow it to appear outside us, then anger will control us." (Seneca On anger ex. 3.13). Seneca states that anger should be hidden in the deepest area inside us and leave it alone. Leave anger and do not let it control us is good for us.
Seneca writes that "Involuntary movements can be neither overcome nor avoided" and "anger is eliminated by the commands of reasons. For it is a voluntary fault of the mind" (Seneca On anger ex. 2.2). We can do nothing about any involuntary things, but as for anger, it can be avoid because it is a voluntary movement. Changing the attitude about unchangeable things, so human will not get angry.
Seneca points out that human getting angry is because we think we are treated unfair. "People judge things to be 'unfair' either because they ought not to have suffered them or else because they did not expect to do so." (Seneca On anger ex. 2.31). Human expect from this world too much and have excessive self-love, so we feel unfair when we get the wrong return. "You should always think that there will be something to annoy you." (Seneca On anger ex. 2.31). Seneca warns us that we need to be prepared in our life so that we will not get anger.
"If a wise man has a duty to be angry at shameful deedsHis entire life will be spent in bad temper and griefHis powers will fail him if he forces himself to anger as often as anger is due" (Seneca On anger ex. 2.7). According to Seneca's view, wise man is easier to get angry than ordinary person, and their anger lasts longer as well. Once they become shameful, their damage to the world will be much more dangerous than a ordinary angry person. He thinks the most scandalous thing is that wise man's state of mind depend on the wickedness of others. Furthermore, Seneca writes out "The wise man will never cease to be angry, once he startshe would lose not just his temper, but his sanity.