•Summon up (one's/the) courage (to do sth) (idiom) - To bolster one's courage.（鼓起勇氣）

Examples:

1.I finally summoned up my courage and went to see the dentist.　　

2.The young soldier had to summon up all his courage to prevent himself from giving up.

•Fall into sth (phrasal verb) - To gradually get into a particular condition; be drawn into a course of action or way of behaving.（陷入，淪於…的境地）

Examples:

1.You must not fall into this common error.　　

2.The classroom fell into chaos as soon as the teacher stepped into the hallway.

•Not to mention sth (idiom) - Used for adding a comment that emphasizes the main idea of what you have already said.（除…之外，且不說…）

Examples:

1.Pollution has a negative effect on the health of everyone living in the city, not to mention the damage to the environment.　　

2.The weather here is gorgeous, not to mention the wonderful food.

•In vain (idiom) - Without success.（徒勞無功）

Examples:

1.It became obvious that all her complaints were in vain.　　

2.We walked on, looking in vain for a taxi.

•In (the) light of sth (idiom) - Because of something; considering something.（由於…，考慮到…）

Examples:

1.In the light of the severe weather, graduation will be postponed.　　

2.In light of this new evidence, we are reopening the investigation.