Be oneself

a person’s self (used for emphasis or reflexively):
one often hurts oneself accidentally.
be oneself,

to be in one’s normal state of mind or physical condition.
to be unaffected and sincere:
one makes more friends by being oneself than by putting on airs.

by oneself,

without a companion; alone.
through one’s own efforts; unaided:
to become a millionaire by oneself.

come to oneself,

also, come to. to regain consciousness.
to regain one’s self-possession; come to one’s senses.

also, come to one’s self.
pr-noun

the reflexive form of one (sense 20), one (sense 21)
(intensifier): one doesn’t do that oneself

(preceded by a copula) one’s normal or usual self: one doesn’t feel oneself after such an experience

1540s, one’s self. hyphenated 18c.; written as one word from c.1827, on model of himself, itself, etc.
act in one’s usual fashion; be in one’s normal physical or mental state. for example, peter’s finally recovered from the accident and is himself again, or i was completely distracted; i just wasn’t myself.
act without pretense; be unaffected, sincere. for example, i really enjoy their company because i can be myself with them.
see:

avail (oneself) of
be oneself
beside oneself
burn (oneself) out
by oneself
cover one’s -ss (oneself)
crank (oneself) up
do oneself in
excuse me (oneself)
exert oneself
explain oneself
express oneself
fall all over (oneself)
feel like oneself
find oneself
flatter oneself
fling oneself at
forget oneself
full of oneself
get a grip on (oneself)
give a good account of oneself
give of oneself
give (oneself) away
give oneself up
have oneself
hear oneself think
help oneself
keep to oneself
kick oneself
knock oneself out
law unto oneself
lay (oneself) open
leave (oneself) open
let (oneself) go
live with (oneself)
lose oneself in
make a laughingstock of oneself
make a name for oneself
make an exhibition of oneself
make a nuisance of oneself
make a pig of oneself
make oneself at home
make oneself scarce
not oneself
paint oneself into a corner
plume oneself
pride oneself on
pull oneself together
pull oneself up
put oneself out
relieve oneself
repeat oneself
shift for oneself
shoot oneself in the foot
spread oneself too thin
suit oneself
sure of oneself
take it upon oneself
throw oneself at
tie oneself in knots
trouble one’s head (oneself) about