Opportunities are missed through too much chatter.
That sheepe that bleateth looseth a bit [mouthful].
[1599 J. Minsheu Dialogues in Spanish 20]
A bleating sheep loseth her pasture.
[1659 G. Torriano English & Italian Dict. 37]
He said something about a bleating sheep losing a bite; but I should think this young man is not much of a talker.
[1861 T. Hughes Tom Brown at Oxford II. vii.]
I thought of reminding him [Churchill] of an adage that I had learnt from my grandfather: ‘Every time a sheep bleats it loses a nibble.’
[1978 R. V. Jones Most Secret War xlv.]
Related to: opportunity, missed; speech and silence
Bibliography of major proverb collections and works cited from modern editions is available here.