A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

be set on doing something • be set to do some-
thing
be set on doing something —be determined to do smth.:
Roberts was outraged, and thereafter he and Nieuwendyk were
set on leaving the team.
be set to do something —be ready and prepared to do smth.:
We were set to enjoy the weekend in a deluxe room overlook-
ing Downtown Disney.
be soft in the head • have a hard head
be soft in the head —(coll.) be foolish or mentally retarded
(also: be weak in the head): One of the curses of being a sci-
ence-fiction writer is that unsophisticated people assume you
to be soft in the head.
Note: 
The expression does not correlate in meaning with the
phrase be weak-minded— be not firm or resolute enough: He
was a good guy, but was manipulated…. I guess you could say
he was weak minded.
have a hard head —be practical and determined, not in-
fluenced by sentiments: He’s not the suit and tie you all think
he is. He has a hard head but he also has a heart.
be sold on someone • be sold out to someone
be sold on someone —(U.S. coll.) be accepted by a person as
worthy: When we first moved in, our neighbors seemed cold
and unfriendly, but now we are sold on them. Cf.: be sold on
something — be persuaded to recognize the worth or desirability
of smth.: Parliament, and presumably the citizens, were sold
on the idea of creating the Child Support Agency.
be sold out to someone —(coll.) be betrayed deceitfully to
smb.: He had little support from the English aristocracy who
felt that they had been sold out to Rome.
be someone’s right-hand man • stay on the right
side of someone
be someone’s right-hand man —act as a person’s chief assis-
tant: I’m counting on you being my right-hand man.
stay on the right side of someone —(also: keep on the right side
of someone) continue to be friendly with smb.: It will pay you
to stay on the right side of the boss, as if you annoy him it
could cost you your job.