If you try as hard as you can, it will breed a good sort of fatalism about being successful. You can't try harder than as hard as you can, and once you're doing everything you can, what's the point of worrying how well you'll do?
You can change what you're doing, apply the same effort, and be more successful. Roughly equivalent to mechanical leverage. Some management types even call it that.
Not sure about it; you might create world-class products, try at your best, it might still not be enough and this sort of thinking after everything-done-right-but-still-failure will kill your motivation forever. Focus rather on making world better, that's an infinite process, and be bold about your focus.
There is such thing as trying too hard. For instance, you could break.