Keep going.

If you build something and it fails, the experience you gain will be valuable - and a failed project is more valuable than an abandoned project - so even if you fail, you'll be in a better position you are in now! :D

Self doubt is normal - it's part of the creative process. But use it to be critical of your own work, but in a constructive way.

If the work seems daunting, remember the words of Dori on finding Nemo - Just keep swimming. How do you eat an elephant? One bite at a time!