The initial idioms of the letter B

be the living end	be the making of
be the marrying kind	be the meat in the sandwich
be the nature of the beast	be the only pebble on the beach
be the order of the day	be the picture of [health etc.]
be the pits	be the salt of the earth
be the soul of discretion	be the spice of life
be the spitting image of	be the talk of the town
be the toast of	be the way to go
be the worse for wear	be the wrong side of 30 etc
be (one's) own master	be (one's) own man/woman/person
be (one's) own worst enemy	be (one's) for the taking
be oneself	be for the taking
Be there or be square	Be there with bells on
be thin on the ground	be thin on top
can't think straight	be three sheets to the wind