Self doubt and feelings of unworthiness indicate that you have forgotten who you are.
In the Indian epic, The Ramayana, when Jambavan, the great king of bears, notices Hanuman meekly sitting off to the side while others boldly brag about their capabilities, he asks this question:
The unconfident Hanuman nervously says,
"You have too much regard for me, good Jambavan."
To which Jambavan replies,
"You have forgotten who you are, Hanuman."
Jambavan goes on to remind Hanuman of his ancestry and that his father is none other than Vayu Deva, the very wind, with all of his wild strength and that Hanuman was destined to doubt himself just as he is destined to then remember who he is, where he comes from and what he is capable of.
As Jambavan lists the humble monkey's many astonishing abilities, Hanuman begins to grow before the entire monkey tribes' eyes, "tall as a hill" and "bright as the morning."
"Every word the king of bears said seemed to sever a link in the chain that bound his spirit. His eyes shone, his back was very erect. Hanuman smiled, and his doubts left him like mist before the sun."
If we take this story out of the literal and into the connotative, we can easily apply it to ourselves. The chains of self doubt and unworthiness that bind our spirit are there to be broken, but some of us grow very attached to our chains and create a story about them that keeps us bound and in some ways, safe. We remain small versions of ourselves and blame as much as we can on circumstances outside of ourselves for this meek existence. Not to minimize anyone's particular journey; some have way more external forces binding them and working against them which makes their self realization all the more powerful.
There is a part of you that knows your own magnificence. There is a voice in your head however loud or quiet that advocates for you even when you are the one putting yourself down. There is an instinct in you that under the right circumstances would toss off these chains of doubt in favor of standing up to injustice for the sake of yourself or another. It is more than mere survival. It is the Knowingness that you are in fact worthy and that your place in this story is essential and that your specific set of capabilities is absolutely vital to evolution.
Some may hear this and choose to stay bound. We have a choice. When we choose to recognize our greatness, we grow like Hanuman "tall as a hill" and "bright as the morning." This isn't about being arrogant or entitled. One can know and acknowledge their Self worth without bragging or putting anyone else down in order to demonstrate it. On the contrary, when you recognize your worthiness, you lift up those around you and help them break the chains that bind them. When you own your own capabilities, you give others permission to own theirs. When you allow yourself to grow, you encourage those around you to grow.
A perfectly delightful and engaging part of the great play of life we are in is that we forget who we are so that when we finally remember, it is a noteworthy catharsis. The drama of Self realization is incredibly moving and unforgettable. As a species, we cheer for those of us who break the chains of self doubt and live the mountainous existence that we know is possible for us as soon as we ourselves are ready. Even if these larger-than-life individuals frighten us a little, like the monkey tribe that trembled as their good friend Hanuman grew, we are also inspired and say, "Lead the way, great one! I am right behind you."