Er on the Side of Yes

I read something yesterday I had never thought of but I do like.  It was said by a guy called Derek Sivers in a book called When in Doubt, Try the Difference.  Someone was quoting him so I do not much about the way he thinks in general, but I like this thought a lot.  “Er on the side of yes.”
Speaking for myself I so know how easy it is to er on the side of no.  No seems to be the default position.  I am definitely not in favour of acting without thinking or giving something due though, but it just seems to me I gravitate to no more easily than I do yes.
By that I mean it seems to be no is so much easier to say.  Especially when yes involves stepping out into the unknown.  Perhaps leaving my comfort zone.  Saying no rarely involves embracing the unknown.  More often than not it seems to me avoiding the unknown.
Embracing the unknown is the only way for me to grow.  Although there maybe times when saying yes involves the familiar, more often than not it involves going places I have never been before.  Being stretched.  Going perhaps from being Mr Knowall to Mr KnowNothing.
To me that is a good way of dealing with pride.  It seems to me one of the greatest hindrance to learning is pretending to know to try to save face.  More often than not I come a cropper down the track in a worse fashion than it would have been if I had just admitted ignorance in the first place.
This is a personal thing, but I have often wondered about a pass being say 50%.  To me that means there is 50% I do not know and is not future proof.  That cannot only be embarrassing but also dangerous.
That is one of the reasons why I think it is good to er on the side of yes.  There is a good chance there is much I do not know in my chosen fields of endeavour.  The proof of knowing is doing.  Sometimes that means leaving my comfort zone and stepping into the unknown.  But the whole reason for stepping into the unknown is to make it known.