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

in one’s mind • on one’s mind
in one’s mind —in one’s thoughts: Miss Quested, who always
said exactly what was in her mind, announced that she was
desirous of seeing the real India.
Note:
The expression is not equivalent in meaning to the phrase
in one’s head
— in one’s memory: I don’t know how the chair-
man keeps all those figures in his head.
on one’s mind —
1
. said of smth. occupying one’s thoughts,
which causes worry or concern: I don’t think I could have slept
anyway because the thought of death was on my mind. 2. =
in one’s mind: Socrates even mocked some people saying to
them whatever was on his mind…
in one’s own right • within one’s rights
in one’s own right—because of personal qualifications: Apart
from the assistance he gave Professor Jones in his research, he
is a distinguished scientist in his own right.
within one’s rights —not exceeding one’s legal or moral
authority: He’s quite within his rights to demand an inquiry.
in one’s own time • in one’s time
in one’s own time —
1
. in one’s lifetime: While in his own
time Terence’s plays were not popular, many critics praised
his graceful handling of the Latin language. 2. in one’s free
time; outside working hours: He wasn’t able to finish the job
at the office, so he had to do it in his own time. 3. (also: in
one’s own good time) at a time and rate of one’s own choosing:
Open learning offers the learner flexible learning opportuni-
ties — the learner can work in his own time.
Note: 
The expression does not fully correlate in meaning with
the phrase on one’s own time—
1
. = in one’s own time 2: My
work as assistant editor is only a sideline. Since I do it largely
on my own time, I avoid extra work and correspondence. 2.
(do smth.) free of charge; without being paid: I answer questions
on my own time. I mean that I do it free of charge, not as