How do you define yourself?

I enjoy reading the Twitter bios people write about themselves. They often tell so much in so few characters. Those bios let you know right away who you're speaking to, what they most likely tweet about and most importantly, how the person views her/himself.

While Twitter is growing and more people are becoming personally transparent, the vast majority of us, even in the social media space, are still trying to become who we want to be. We are projecting who we want you to know, how we want you to perceive us and the manner in which we want to communicate. So what, people have been studying this for years. We all have up walls, let certain people see certain sides of us...big deal. In fact it is a huge deal, what happens when our perception of ourselves, however true or contrived, comes crumbling down?

Let's look at a case study:

Delia considered herself a career woman. She had worked her way up the corporate ladder and had the trophies of success. When she found herself laid off and unable to find a comparable position after several years of searching, she was devastated. Her career defined her, and when that was gone, she didn't know what to do with herself.

She lost her home, down-sized to an apartment and eventually lost everything she had put in storage. She let go of her social life, claimed she was "too tired" to do this or that. She retreated into her apartment, not going anywhere or doing anything. She fell into depression and even considered suicide at one point.

Her friends prayed with her and for her. They shared what they had with her and continued to love her as they had always done.

She eventually got a new job and began to put her life together. Her decade long ordeal changed her perception of herself to one that isn't reliant on external forces, but is based on internal gifts, talents and abilities.

How do you define yourself?
Is your perception of yourself dependent on external things?
If thing(s) were to change, how would your self-perception change?