Not sure I'd want to write about 'everything' but agree about the imagination. I'm sure we all go through periods of self-doubt. I know I do (especially with the story I'm trying to write at present!)
Self-doubt is definitely a killer!
Self-doubt is my companion. I'm in good company.
I think there's definitely the germ of an idea in anything and everything around you. Even the simplest thing can spark the muse.