Anger is rarely looked upon as a beneficial character trait, and is usually advised to reduce it.

这是 2018 年高考英语北京卷阅读理解七选五的一个句子。请问后面部分 is usually advised to reduce it 的省略的主语是什么？是 anger 吗？讲不通啊。再一个就是，句末的 it 指代什么？

附完整材料如下：

Why Do We Get Angry?

Anger seems simple when we are feeling it, but the causes of anger are various. Knowing these causes can make us examine our behavior, and correct bad habits. The main reasons we get angry are triggering（触发）events, personality traits（特征），and our assessment of situations. ___51___

Triggering events for anger are so many that to describe them all would take hundreds of pages. However, here are some examples：being cut off in traffic, a deadline approaching, experiencing physical pain, and much more. ___52___ The reason why someone is triggered by something and others are not is often due to one’s personal history and psychological traits.

Each person, no matter who they are, has psychological imbalances. People who have personality traits that connect with competitiveness and low upset tolerance are much more likely to get angry. ___53___ Also, sometimes pre-anger does not have to do with a lasting condition, but rather a temporary state before a triggering event has occurred.

___54___ Sometimes even routine occurrences become sources of pre-anger, or anger itself. Sometimes ignorance and negative （消极的） outlooks on situations can create anger.

___55___ However, anger can easily turn violent, and it is best to know the reasons for anger to appear in order to prevent its presence. With these main reasons in mind, we can evaluate our level of anger throughout the day and prevent cases of outbursts by comprehending the reasons for our feelings.

A. Our attitude and viewpoint on situations can create anger within us as well.

B. But some types of situations can help us to get rid of the occurrence of anger.

C. Anger is rarely looked upon as a beneficial character trait, and is usually advised to reduce it.

D. Anger is a particularly strong feeling and maybe people think that they have reasons to feel angry.

E. Having these personality traits implies the pre-anger state, where anger is in the background of your mind.

F. Understanding these reasons will control our own anger if we are willing to evaluate ourselves with a critical eye.

G. Not everyone acts the same in response to events, and that is why what triggers one person may or may not trigger another.