Do you want to write fiction or stick to real life stories? Sometimes you can get inspired by a story close to you--and that's the easiest story to write. It's always best to stick to what you know. If you want to write fiction, use the same principle. Draw from your real life experiences to flesh out your story.
Self-publishing is designing and writing the book yourself, then paying a printer directly to have copies of the book made instead of leaving it to a publisher.
Typically a publisher will buy your story, and then makes all the arrangements for illustration, finished size, font selection, etc--so you sometimes don't have a lot of say in how it's done. If you opt for royalties instead of a one-time payment for your story, you make pennies on the dollar on each sale.
Also, it often takes a year or more from the time the publisher decides your story is print-worthy and the time the book comes out.
Self-publishing allows you full control on the final product and doesn't have to take as long from start to finish, but since you're paying up front and working alone, to make any money, you have to market the book yourself and sell a lot to make a profit.
It's a sort of 'damned if you do; damned if you don't' situation.