After spending weeks and months and sometimes even years on a book, is there any feeling in the world more exhilarating than writing "The End" and then throwing up your hands in the time-honored cheer of victory that is recognized the world over? For an author, it's like chocolate and Christmas all in one.
In fact, I love writing the end so much that I often race toward it a whole lot faster than I should. I see the conclusion coming, I wrap everything up in a neat bow, I do the dance of the awesome . . . and then I realize that I did it again. I rushed the ending, and it's not going to be satisfying to the reader.
When you invite the reader into your world, you are creating an experience for them. You're asking them to invest emotionally in the story you're telling. You encourage them to fall in love with your characters. By the time they've been through every peak and valley and adventure with those characters, they very much want to know who succeeds and who fails, and they want that sigh of satisfaction at the end. Rushing the ending is like handing them a bowl of Jell-O when they've been anticipating chocolate cake all during the meal.
(Yeah, I'm using a lot of food metaphors ... chocolate metaphors ... but I'm on a diet and I've already lost two pounds since yesterday, so we'll just deal.)
As you reach the ending, check to make sure that you've answered all the story questions. Slow down the declaration of love or the discovery of the treasure or the solving of the crime just a little bit and let the reader savor the moment. Don't drag them out forever - that's annoying too - but give your reader enough to sink their teeth into. This is their payoff for having given you so much of their time.
Now, if you'll excuse me, I have an ending to write. Of course, I can't really write an ending until the book is finished ... so if you'll excuse me, I have a book to write.