Multiple projects for side income instead of one

I've been attempting to work on side projects but most of them only yielded little profit. I soon realized that I don't have the magic touch to make one project go viral.

Recently, I realized that I might have more luck doing multiple things at the same time. Perhaps sell gadgets, self-publish a few books, a few Android apps, provide various services and so on. Hoping the sum would make something worthwhile.

Although right now my goal is to supplement my income, I'm dreaming that one day I'll be able to quit my day job and work for myself. Ideally having the entire day to work on these things.

I'm curious about how some of you succeeded with one big project and others with multiple smaller ones.

My ambitions sometimes grow too big and maybe this is just a pipe dream.

Your opinion would be appreciated.