However, this can also be an opportunity to gain some understanding about our nature and our minds. Through that understanding, we can free ourselves from suffering, find joy, and embrace life and the present moment as it is.
I am just finishing the book The Power of Now by Eckhart Tolle, and your comment made me think about what is explained in it. Tolle talks about how much of our suffering comes from how deeply we (understandably) tie our core identity and self-worth to our external skills, our past achievements, and our status among peers.
He explains that our minds construct an ego, with which we identify. To exist, this ego needs to create and constantly feed an image of itself based on our past experiences and achievements. Normally we do this out of fear, in an attempt to protect ourselves, but the book explains that this never works. We actually build more suffering by identifying with our mind-constructed ego. Instead of living in the present and accepting the world as it is, we live in the past and resist reality in order to constantly feed an ego that feels menaced.
The deep expertise you built is real, but your identity is so much more than just being a 'principal engineer'. Your real self is not the mind-constructed ego or the image you built of yourself, and you don't need to identify with it.
The book also explores the Buddhist concept that all things are impermanent, and by clinging to them we are bound to suffer. We need to accept that things come and go, and live in the present moment without being attached to things that are by their nature impermanent.
I suggest you might take this distress you are feeling right now as an opportunity to look at what is hurting inside you, and disidentify yourself from your ego. It may bring you joy in your life—I am trying to learn this myself!