let one's hair down

let one's hair down (forget all your inhibitions; to relax and enjoy yourself because you are in a comfortable environment) — расслабиться, отбросив условности; перестать стесняться; вести себя непринуждённо или развязно; отбросить условности; ~ оттянуться по полной программе

Example 1: Just take time out from your relentless work ethic and celebrate life. You are unusually bold in love now, too, as passions are high. When you let your hair down, there are no half measures. (Horoscope)

Example 2: We need a place where young folk can let their hair down and enjoy themselves. (MM)

Example 3: Go on! Let your hair down for once and have a blast.

Example 4: Well, I've had it up to my ass with sedate! You said you and me was gonna get outta town and, for once, just really let our hair down. Well, darlin,' look out' cause my hair is comin' down! (Mv.: "Thelma and Louise")

Example 5:
Ms. TWAIN: We get together for barbecue.
Rep.: I'm just wondering, I mean, does everyone kind of let their hair down a little bit?
Ms. TWAIN: Absolutely. When we simply get together as families, we let our hair down and we talk about everything that -- you know, regular people would talk about.
(ABC_GMA)

Related vocabulary:
[оттягиваться]

[don't sweat the small stuff]
[simmer down ]
Don’t sweat it!
Don’t worry about it!
Relax.
Take it easy.
Hang loose. (slang for “take it easy”, relax)
Mellow out.
Chill out.