Some experience I can share when dealing with complex projects (not only coding projects, but in general).

A lot of projects seem easy but are complex in nature. Complex doesn't mean it will be difficult but it needs attention.
I have always learned to study a problem first and think about how to split it up into managable parts.

Don't set your goal on the completion of the whole project. Set your goal on the completion of one milestone. This way you will be interested in the project much longer because you get a lot more rewards when working on it.