Although I promised myself that I would only spend the first five steps on the actual writing process (I’m sure I’ve given enough steps, examples and advise for new authors to feel out the start of a story for themselves), this will be the last one, which I would need to write entire an book to give an example for… and I will be working on that anyway ;).
Whether or not you decide to continue your story can all be up to where the story might go and whether or not you want to follow it. I generally go by word count: if you’re feeling cold feet before 10,000 words, try to conclude it as a short story and move onto another idea. If you manage to get passed 10,000 words, there must be something in that that you find interesting, follow that interest and see where it leads you. If you get to 50,000 words, finish it, that’s a novel. If you go over that, then do so, so long as you conclude it.
My sixth piece of advice for continuing a story: write toward a goal. What is a scene or imagery that you want to get to? Think of every part of the story leading to that is merely just steps toward this scene that you really want to write. This is why I honestly believe that writing to an end is a more satisfying and motivating way to write. In other words, if your story goes from A to B, try to make B a more appealing thing to write than A. Otherwise, once you’ve written A, you’ll be less compelled to write all the way to B.
Is the beginning what you really wanted to write? If so, maybe your book will work better as a short story, but remember that these are harder to get published. Write to an ending that you really want to write and spend the 50,000 words in-between giving emphasis to the characters and scenes so this ending will have more of an emotional impact on the reader.