Functional programming is based on a set of concepts and principles that may differ from what you are used to in other paradigms. For example, you need to understand what a pure function is, how it differs from a side-effecting function, and why it is important to avoid mutating state. You also need to understand how to use higher-order functions, such as map, filter, or reduce, to manipulate data without loops or variables. You need to learn how to use recursion, tail calls, and continuations to implement control flow without iteration or branching. You need to familiarize yourself with concepts like currying, partial application, closures, and combinators, and how they can help you create modular and reusable code. You need to grasp the idea of functional composition, and how it can help you create complex functions from simple ones. You need to know how to use data structures like lists, tuples, records, and variants, and how to work with them using pattern matching, destructuring, and lenses. You need to explore the concepts of monads, functors, applicatives, and other abstractions that can help you deal with effects, errors, state, concurrency, and other challenges in a functional way.