a brick picked up to knock on the door and thrown away when it has served its purpose--a stepping-stone to success

fleece(make somebody squeal)

have boundless prospects

One man's fault is another man's lesson.(Other people's defects are good teachers.)

lighter than a feather

A promise that will be kept.(be true to one's word)

He who rides a tiger is afraid to dismount.(be in for it; have a wolf by the ears; have no way to back down)

too high to be popular(highbrow songs find few singers)

sinister in the extreme

be unwilling to throw away(not bad enough to throw away)

easy to undertake

find one's match

waste all the previous efforts

only once in a long time

bring sb. back from death

most welcome(all that one could wish for)

try what you have devised against others

have a meteoric rise

mutually to make up their deficiencies

in a most dangerous condition