In the end, every complex task is made up by a lot of simple ones.
Always do research before starting on the actual development. It will clear up a lot of things on the very beginning. Helps you create milestones (goals), which can give you confidence when you reach them. The more you practice this, the easier it will be to see the details in new projects in the future. Helps you create an analytical mindset.
I think everyone suffers from this, from time to time. Only practice can help you overcome this.
I had the same feeling a couple of months ago with a brand new project, with lots of tech I haven't used before. But we (another dev and myself) sat down and spent a month with research. We wrote numerous documents on every aspect of the project. Spent a week in a meeting room shelling out the design and how things will fit together. It was a priceless experience.
Highly recommend the R&D approach. We are engineers and it seems so many times we fail to do the R(esearch) part of our work. We just jump right in and drown in the middle of the complexity we face.