make a mistake

To "make a mistake" means to do something wrong or incorrect. This can be used for a lot of very different kinds of situations, including:

• getting the answer to a homework question wrong
• cheating on your husband
• telling a coworker the wrong information

Tell me the truth: (question)?

Use this phrase when you want someone to give you an honest answer instead of just speaking politely:

A: Tell me the truth: do you think that Kiki can really handle this job?

B: Well, to be honest, I think she might have a hard time with it.

You use "Tell me the truth..." mostly with friends or people who you know well. 

as (someone’s) friend

Saying “as my friend” means you have high expectations from your listener. Use this phrase to point out how, because you are a person’s friend, your opinions are important to each other. 

As my friend, you should have defended me.

You can also say "as your friend" to talk about yourself:

As your friend, I care about what happens to you.

Notice that “as (someone’s) friend” almost always is at the beginning of a sentence, because it’s an introduction for what comes next.

a huge mistake

The word "huge" is often connected to "mistake". "Huge" means "big". Some other adjectives that often describe mistakes include:

• a big mistake
• a terrible mistake
• an honest mistake
• a common mistake