Finding Significance

Growing up my dad and I always exchanged books with each other, so when I visited home last weekend my dad sent me off with a new book. I started reading the book on the plane and have been reading it for the past week, but today I read a chapter that really intrigued me.
The author examines the things that humans find their significance in. These things ranged from relationships, career, sex, financial security, family, personal freedom, etc. Anyways, the author argues nearly anything that a person attempts to find their significance in is dangerous.
One suggestion that the author gives in diagnosing what one finds his significance in, is to ask this question: Is there something that will keep you up at night and throw your into paralyzing anxiousness?
I recognize that for me I find my significance in my career. I remember those sleepless nights in college simply fretting over my job prospects. What do I have to do achieve a GPA worthy of a BB? Am I networking enough? Anytime I perceived something threatening to my job prospects, I would be hurled into a brief depression, feeling wildly anxious about "what am I doing with my life?" (This is not to say that a healthy dose of fear is not necessary)
The author goes on to explain that even if you achieve what you set out to achieve, you will still feel insufficient. He gives the example of a movie star who formerly worked the make up counter at Macys, and when she finally achieved her fame, she became more depressed because despite having all she wanted, she was still the same person and it never satisfied.
I can identify with this on a small scale. I got the job I wanted, and I love my job, but it is not all that I thought it would be. I still feel the same way I did even before I got my job.
Even if you place your significance into something seemingly nobler, such as family, you are in for a rough go. The author speaks of a mother who placed her significance in the happiness and success of her son. When her son began doing poorly in school, she saw it as a reflection on her own person. She became angry with her son, and began hating anything that threatened her son's success. She began to loathe and blame her husband for her son's failings, which to her was an attack on her own self-worth.
An interesting example the author gave came from the movie Chariots of Fire. When asked why works so hard to run the 100 yard dash, a runner explains that from when the gun pops, he has 10 lonely seconds to justify his existence. I think we can all identify with his feelings in some way.
We all find our sense of self-worth in something, and that something will always be threatened. Even if we do achieve what we wanted, is it enough? Is there a secure thing that we can find our significance in? What do you guys think?