We underestimate ourselves when we accept limitations and don't notice. Our assumptions go invisible on us. They stop looking like assumptions and simply look like the truth. We then act accordingly.
Personally I know that I have at times hugely underestimated myself. I only saw how invisible this was when kind friends pointed it out to me. But it's not easy to hear. Ever witnessed someone defending their limitations? Maybe you even tried to talk them out of it when they asserted they aren't "the kind of person who..." or "tried but can't..."
I don't have any trouble calling to mind someone I know who can't quite see for themselves just how attractive, strong, capable, loving or giving they are.
A quote attributed to Henry Ford is
Whether you think you can
or whether you think you can't
you are right
The whole package that makes up what I call "myself" is only a mystery to one person: Me. And it's amazing how wrong we can be about our own base assumptions of who we are.
Underestimating yourself always arises from who you assume you are.
The question "who am I?" deserves more airplay than we give it. Not only are we not entertaining the question, we seem to be moving away from contemplative traditions in which these kinds of questions mattered. We no longer engage in pure inquiry. Are we so intolerant of mystery that we would rather be wrong than not know something.
The price we pay for this is to be overly-engaged in our assumptions. And from the assumption that there is something fundamentally limited about us arises the desire to improve who we are.
Why improve who you think you are when you can simply look to see who you really are "before" the personality arrived that you call YOU.
"Who am I" or better said, "What is I?" are invitations to peek underneath the construct of ourselves, beyond the false self that we made up and just see. What came before the thoughts of "I."
I have come to appreciate these contemplations, and to enjoy following where they lead.
Are you the limited person you think you are? What if you are not?
This self I call me seems nothing more than a bouquet of thoughts, rather than facts. I call them me, but really they are air. They are concepts -- ideas that have nothing to do with who I am or what I am capable of -- if I weren't so interested in what I think about myself.