To Shape Up

EXAMPLE  1:

Dear Zora,

This is the last time I will remind you to wash the dishes after cooking.

We are roommates and we share a space. You never clean up after yourself! I always have to ask you to keep the apartment clean... Sometimes I feel like I am your mother! Seriously, if you don't shape up, I will ask you to leave. 

Sincerely,

Tasha Orushko

EXAMPLE 2:

Dear Tasha,

I don't care what you say! I pay my rent on time and I always wash the dishes!

I am not your maid. I will clean up my mess, but don't expect me to pick up after you.  Am I clear?

You are the one who has to shape up, my friend!

Have a great day!

Zora

MEANING: To shape up means to improve performance or behavior 

http://languagesystems.edu/

In Over one's Head

Example 1:
I want to graduate early, so I registered for 2 extra classes this semester. I thought I could handle it, but I'm starting to think I am in over my head. With all the homework, reading assignments, and classes to attend, I'm not sleeping well and I'm feeling overwhelmed. The deadline to drop classes is next week. I'll probably have to drop one to make things more manageable.

Example 2:
My new job just started. It was probably a terrible idea to lie on my resume about my experience. Now my responsibilities includes skills that I don't actually have. I'm totally in over my head. I will have to be honest with my boss and let them know that I'm not actually qualified for this position. 

Explanation:

To be in over one's head is to be overwhelmed by something you can't handle. Usually a person puts themselves into this situation.
In Example 1, this student has registered for too many classes. The workload has become a problem. It is more than the student can handle.
In Example 2, this person gave false information to her employer, now they have responsibilities that are beyond their knowledge and experience. They cannot handle their job. 

Use the be  verb with a possessive pronoun to form sentences.
I am in over my head
She/He is in over her/his head
We are in over our heads
They are in over their heads 

http://languagesystems.edu/