Your story's ending is the final determination of whether the reader will go on to read more of your books or move on to another writer. The more compelling your ending, the more likely the reader will buy your next book.
Every first draft will turn out differently depending on the writer's process. Some people outline every little detail beforehand, while others go with the flow. There are no set rules to follow. So, the only goal you should have in mind is to finish the story.
It can be difficult to tie up all your loose threads if you can't remember them. Outlining can help you pace your ending and keep the event order straight as each unfolds. Think about your climax's impact and how everything needs to come together for a powerful ending.