"Until you make the unconscious conscious, it will direct your life and you will call it fate.", Carl Jung
Jung's idea was straightforward: the qualities you refuse to accept in yourself get projected externally onto others. If, while growing up, your parents taught you that anger was unacceptable, and you repressed it, you can become intensely judgmental of angry people. Your inner anger becomes a shadow self you don't want to face, so you externalise it instead. The things and people that trigger us most often represent an external version of our own inner shadow.
We can also repress positive qualities such as creativity, ambition, power, sexuality. Anything we were taught was "too much" gets pushed down alongside the things we were told were "not enough." The shadow holds gold as well as darkness, which is why the work isn't just about confronting what you fear. It's also about reclaiming what you've abandoned.
To fully individuate, or integrate the shadow self in Jungian terms, we need to make the unconscious conscious, face what we fear, what we reject, and what we consider too much. It often requires brutal honesty to recognise that we shouldn't blame others or the world for our triggers, but take ownership of them instead.
If you've spent years in therapy, meditation, or coaching and you're still repeating the same unconscious patterns, this is probably the layer that hasn't been touched yet.