Will the brave knight slay the dragon and rescue the princess? The answer to that is a single word: Yes or No.
How will the brave knight slay the dragon and rescue the princess? Now that is an interesting question. I could write a story based on that.
This post is about the importance of the "HOW" in a story, at the expense of the "IF". By this I mean, that whether or not the protagonist succeeds in what ever endeavor they set themselves to or what conflict they have to overcome is not as important as the conflict itself. It's like that old saying "It's the Journey that counts."
"Happily ever after" is as boring as "rocks fall, everyone dies". Furthermore, they are short and endings. While necessary to complete a story, they are not what the writer should be focusing on and/or stressing out about. I don't know anyone who picks up a book simply to see the ending, and skipping to the ending is likely to be confusing because you won't have the frame of reference to make sense of it. As an example, I will use the anime BACCANO!. The first episode spoils every single plot point of the main storyline in the first few minutes, but unless you know who these characters are and what's going on, it won't mean anything to you. The appeal of the series is watching the shenanigans that lead up to that point.
Readers are savvy. On Tvtropes, we have numerous tropes describing this predictability: The Good Guys Always Win, Underdogs Never Lose, Third Act Misunderstanding and Break Up Make Up Scenario. It takes a great deal of skill to legitimately make them think that the secret agent will perish in the death trap, or the hero will be killed by his arch enemy, etc. Whether then base the tension of your story on whether or not the Good Guys win or the underdogs win the big game or the two leads hooking up, focus on the struggle to get to that point.
For another example, I will use the light novel and anime "No Game No Life". The two leads are a brother-sister team calling themselves "Blank". They begin the show as a gamer of god-like skill and their motto is "Blank Never Loses". The appeal of the show is not in the tension of whether or not they will win or lose (though there is plenty of that) but rather it's in the cleverness of their strategy and the frequent humor (also, the animation is gorgeous). If the point was simply for them to win, it would get old quickly. Thus, there is more to it.
Another example is the manga and anime "Hellsing". Here I'm specifically referring to "Hellsing Ultimate". The "hero" of this story is the brutal vampire Alucard who works for the Hellsing Organization in killing supernatural threats like ghouls and other vampires. There is no tension in Alcuard's fights at all. He outclasses all of his opponents so much that the question is not "will he win?" but "how bloody and creative will he make his opponent's death?" He has to be absent for most of the series' climax because otherwise there is no doubt he would quickly resolve it. Thus, you get to the see the other, less powerful, heroes being awesome.
One final example from one of my favorite fan fiction authors will due to prove my point. "Brave New World" by Ri2 has the most generic of premises: A couple of heroes journey to find mystical trinkets to stop an evil organization from destroying the world. What makes this fiction special is happens within the context of that premise. There are astounding twists and turns, uproarious funny events, and a tremendous amount of original world building. None of this has more than tangential relation to the premise. Most of the time it's there for Leo, resident Genre Savvy nerd, to make fun of for being generic. At times it feels like an excuse plot.
When writing your stories I encourage you to keep these examples in mind.