Humbleness is all about timing.
To manifest the vision of the world which you wish to create, sometimes all you have to do is step out of the way and let it happen. If you trust the world and the people around you, life does not need to be a struggle.
If you are aligned with the pulse of the world, you have a feel for when it's better to assert you ego and when it's better to be humble.
Developing humbleness into an attitude (where you always avoid confrontation and always step aside) draws on your strength and limits you to living a life others choose for you.
To deprive the world of your strength and beauty is a waste, crime and/or sin - pick the ones that suit your world-view.
Most people who try to follow humbleness to the extreme become not truly humble at all; they simple move their ego to a moral high ground and leave it there to get bloated.
Practicing the attitude of humbleness is efficient if you have ego issues. This path can help you work at self-discipline, which in turn would help you learn about the balance and timing necessary for true humbleness.
Live and let live!