There are a lot of simple examples right in `Control.Monad`. As soon as I know that something provides the `Monad` interface, I know that I can use things like

There are a lot of simple examples right in `Control.Monad`. As soon as I know that something provides the `Monad` interface, I know that I can use things like `mapM`, `foldM`, `replicateM`, `filterM`, `forever`, `sequence`, `zipWithM`, the list goes on... Certainly not all of these are useful in every case - eg. `forever` needs your action to do something or you're just hanging forever. But it's a toolbox that's easy to reach for, and which applies to a large pile of things. And when you can structure a new function only in terms of things in that toolbox, you've added another thing to the toolbox. See, for instance, `monad-loops` for more. Exploring pairs of utility function and Monad instance can be interesting, asking (eg.) "what does `unfoldM` mean when I use it with `State`?"