I’m sure I have heard it said that a story needs a beginning, a middle and an end. This may seem obvious, but it is a good structure to work with and ties in with a well known writing technique called the Three Act Structure. The idea is to have 3 major problems. The first should fill the first quarter of your story, the second should encompass the next two quarters and the final major problem should take you through to the climax at the end.
Problem one should set your protagonist on the path of their fate and the following problems should become progressively worse. You can throw in smaller side issues as the story progresses, but their severity should not surpass any of the major problems in the story. Your ending should result in a win, lose or draw that will create a “Yes!”, “Noooooo!” or a Yes but No/No but Yes reaction from your reader.
Try it and see how it works for you.