As a new developer, I think I fall into this trap a lot! I always don't want to touch other people's methods or introduce bugs, so I only make tiny, tiny little changes before thoroughly testing everything. It really slows me down.
Second, the slowness comes from the fact it takes a lot more time to read and understand code that to write it, let alone trust that it is doing what is doing correctly. If you don't introduce bugs and are very careful you won't have nightmarish surprises. Keep up.