What usually helps while learning a concept for the first time is thinking about related problems in terms of how you would prove correctness of your solution, which is induction in this case. If you understand induction and how it is just the mathematical analogue of recursion in computer science, you'll be able to code recursion faster. Of course, it becomes easier only with practice/experience, so it is always a good thing to solve a lot of problems.

practice, after a lot of repetitions it will become automatic and you can focus on other parts of the problem (or modifications to your trees)