When faced with a complex task it can be easy to get overwhelmed. This can lead to “analysis-paralysis” where your mind is constantly trying to figure out every possible outcome or variation. It can often be easier to focus on one detail and get that working as simply as possible. Maybe you only implement the “happy path”. Maybe you only implement the path that fails. Either way pick the easiest solution to implement first. Get that working. Then build on your success and tackle the next part.