hang loose

hang loose AND stay loose (to remain relaxed or calm; relax, take it easy, have fun and don’t worry about anything; || to become free, independent, etc.; to revel without restraint ) — расслабиться, хорошенько отдохнуть; оттянуться;| ~ пуститься во все тяжкие
cut loose

Example 1: Try to hang loose and don't let it bother you. (dictionary.reference.com)

Example 2: Just hang loose, man. Everything'll be all right. (dictionary.reference.com)

Example 3: (Just) stay loose, bud, and it will all work out.

Example 4: a Let's cut loose after work and go out for a drink.

Example 4: After the meeting we headed into town to cut loose.

Related vocabulary:

[don't sweat the small stuff]
[simmer down]
[let one's hair down]
Don’t sweat it!
Don’t worry about it!
Take it easy.
Mellow out.
Chill out.
не парься
не запаривайся