We introduce a technique for programming with domain-specific linear languages using a monad that arises from the theory of linear/non-linear logic. In this work we interpret the linear/non-linear model as a simple, effectful linear language embedded inside an existing non-linear host language. We implement a modular framework for defining these linear EDSLs in Haskell, allowing both shallow and deep embeddings. To demonstrate the effectiveness of our framework and the linearity monad, we implement languages for file handles, mutable arrays, session types, and quantum computing.