Star Wars is a worldwide phenomenon today and one of the biggest franchises in history, so it's difficult to imagine that when the film was being produced hardly anyone, at times not even the director, had faith in it.
We think this fact is more inspirational that any number of cat posters that urge you to "hang in there," or even the "Daily Reason To Be Happy" Tumblr. C'mon. If George freaking Lucas had doubts about Star freaking Wars, then you can feel a little more optimistic that your passion project/ Etsy shop/ English midterm will turn out a-okay.
Looking Back, Moving Forward
Before Star Wars, Lucas had only directed two other feature length films. The first was THX-1138, an experimental dystopian science fiction film released in 1971. Never heard of it? Yeah, didn't think so. The second was American Graffiti in 1973, which was a tale about hot rodding in Northern California in early 1960's… and about how awesome doo-wop music is.
Both films have tenuous connections to Star Wars. THX is science fiction but of a different vein, and American Graffiti draws from Lucas's childhood love of cars similarly to how Star Wars draws from the films Lucas loved as a child. However, that's where the connections end.
As a director and screenwriter, Lucas created a patchwork world, combining pieces of the cinema that influenced him. The opening text crawl and the fantastical space ships were inspired by 1930's serials like Flash Gordon. The lightsaber duels and wipe transitions are taken from Akira Kurosawa's Japanese historical period films. Luke and Leia's daring escape from the Death Star is from an Errol Flynn swashbuckling adventure. The Mos Eisley Cantina is a western saloon plus gritty Muppets. Even C-3PO has its origins in Maria's robot double from Metropolis.
None of this is to say that Lucas's vision wasn't original, but in creating an original style, Lucas drew from the films he loved, and his stylistic choices reflect this. Basically, Lucas was doing what Quentin Tarantino would do a couple of decades later—take from existing work and make it his very, very own.
Star Wars also demonstrated Lucas's love of pushing the technology of cinema forward, a goal that would become of the focus of his entrepreneurial and producer career at Lucasfilm Ltd.
Fighting the Good Fight
Lucas had to fight to make Star Wars in the way he envisioned it—or to get it made at all, for that matter.
The director is famous for not wanting studio executives to mess with his films, having become upset over the changes Warner Bros made to THX and Universal to American Graffiti (source). With 20th Century Fox footing the bill, Lucas had to fight tooth and nail in order to not bend to their (sometimes weird) requests.
Mark Hamill notes an oddball example:
Some of the thinking from the suits, as they call them, was so strange. We were in our fifteenth day of shooting, and I'd read over somebody's shoulder and I'd see a missive that said, "Can't you put some pants on the Wookiee? (Source)
While fighting meddling execs, Lucas also dealt with production setbacks on basically every front. The on-site production in Tunisia was hampered by massive rainstorms on the first day of shooting and the sheer amount of work led to doubts among the crew (source). Industrial Light and Magic were so far behind schedule on the special effects that only one special effect shot was finished by the time live action wrapped up.
(To be fair to ILM, they had to invent the techniques and equipment they were using to film.)
Despite the numerous, super-stressful trials, Lucas was able to complete Star Wars, and it became the highest grossing film at that time and was nominated for ten Oscars, bringing home seven of the little golden men. Not too shabby for a science fiction film that was prophesized to be dead at the box office.
The success of Star Wars didn't lead George Lucas to become an independent filmmaker, and he wouldn't direct another film until The Phantom Menace in 1999. Between that time, Lucas took up producing and entrepreneurial efforts, ironically becoming the studio exec he had always battled against.
Never Ending Story
Since its release, Lucas edited and tweaked the film to be more inline with his vision. The first chances appeared in the 1981 re-release of the film, and Lucas made minor-to-major changes for the film's various home releases. The most drastic and controversial of these revisions came in 1997 when Lucas re-re-released the entire Star Wars trilogy into theaters under "the Special Editions" label.
In Star Wars Episode IV: A New Hope, Lucas reincorporated entire scenes lifted from the editing room floor, including a confrontation between Han and Jabba the Hutt and a reunion between Luke and his childhood friend Briggs Darklighter.
Lucas also added digital effects to the film, some incidental, others completely altering scenes. The most controversial of these came in the Mos Eisley Cantina when Han Solo was confronted by the bounty hunter Greedo. In the 1977 cut, Han Solo shoots Greedo from under the table without giving the bounty hunter warning or a chance to fight back. In the Special Editions, Greedo shoots first and Han's blast is in self-defense. Displeasure with this change led to the famous proclamation by fans that "Han Shot First."
Pro-tip: never, ever enrage die-hard Star Wars fans. It doesn't end well.