A temporary agreement (or arrangement) that allows the parties involved to have semblance of peace until a permanent solution/settlement can be worked out.

A way of getting along together that doesn't require either of two disputing parties to compromise [''Compromise is usually the only solution, one or all must compromise at some point, and it is usually only one that does and not all.''].

Literally, "Way of living" as the accommodation allows the disputing parties to get on with their lives.

Why couldn't I get this to work in my last marriage?

''Because, marriage requires both disputing parties to compromise?''

"Way of living" = morals, scruples, values, attitudes, etc., and these can be where the real conflicts arise from.  "Modus Vivendi" sounds much easier then it is in many cases, because it requires cooperation and a willingness to communicate.  When it works, it works.  When it doesn't work, it really doesn't work.  Rational thinking by all parties is rare in disputes, and where rationality exists, disputes are rare.