Look at writing as a chance to build. To build anything, you have to be willing and ready to sit still and build, brick by brick....piece by piece...word by word!
Thinking about anything from a big picture perspective can be overwhelming after a while. It can be encouraging to get a glance or glimpse of what's to come. But to try to dwell on the vastness of the end goal while staring at the materials that aren't yet put together, as evident progress can be counterproductive.
See the end from the beginning and be encouraged. Then, be present for the materials in front of you - the pen and paper, or the empty page, so that you can move toward that end, and not just keep seeing it afar off.
Your words are your bricks. Build.