Training neural networks is an art rather than a process with a fixed outcome. You don't know whether you'll end up with working models, and there are many aspects that may induce failure for your machine learning project. However, over time, you'll also learn a certain set of brush strokes which significantly improve the odds that you'll succeed. Even though this may sound weird (it did when I started my dive into machine learning theory), it think that the above description is actually true. Once you'll dive in, there will be a moment when all the pieces start coming together.