Tranquille!

peinard(e) = cushy, snug, quiet. The 'd' is silent except in the feminine form. Considered slang, but widely used and wouldn't shock anyone I know - even though that probably doesn't mean much...
J'ai un job peinard = I have a cushy job
Je suis peinard! = I take things easy!
Tiens-toi peinard! = Stay out of trouble!

Another expression I like that comes to mind is se la couler douce - to take it easy (literally to flow softly)
il se la coule douce au boulot = he takes it easy at his job (un boulot is slang for job)