a good (category of person) (does something)

This is a way to talk about how someone in a certain position should behave:

A good chef always keeps his kitchen spotless.

A good athlete never gives up, no matter how far behind they get.

a simple message

One meaning of the word "message" is an idea that a person tries to get other people to understand and believe. Politicians, authors, religious leaders, and business executives have "messages". You can talk about someone's message like this:

Her main message is that people need to incorporate movement into their daily lives, not just spend an hour at the gym every few days.

A "simple message" is one that is clear and easy to understand. This phrase sounds very positive.

Their message is simple: they want to reduce the size of the government.

again and again

Instead of just saying "again", English speakers sometimes say "again and again" for emphasis. "Again" might mean just one more time, but "again and again" means many times.

You have to do it again and again until you get it right.

the power of (something)

English speakers sometimes talk about "the power of ___". We use this phrase to talk about an abstract idea that is important and can have a big effect on people. Some common things that we talk about "the power of" include:

• the power of love
• the power of positive thinking
• the power of prayer

Here's an example from one of the Star Wars movies:

Never underestimate the power of the dark side.