For any project you work on, it can be overwhelming when you see it as a whole.
For example, setting up a water treatment system or building a shed.
To combat that feeling, take at least a step daily.
Every. Single. Day.
Do one thing to move the project forward. Large or small. Just one thing. You might even get into the groove and do more.
Start with the big project and break it down into smaller and smaller steps. Work backwards from that.
If you're building a shed, you first have the foundation to do. There are many steps just for that, so it can be broken down further.
Marking location, digging, compacting, adding gravel, concrete form framing, rebar and finally pouring.
That might seem like a lot, but you don't do it all in a day.
One day you mark out the location. Then you start digging to the depth you need. Another day you add gravel and compact it all.
You obviously don't have to do only one of these a day. Some of these things only take minutes.
The point is that you do something to move forward on the project each and every day.
One thing that might help would be to write it down. All the parts that make up the whole project.
Just go down the list one by one, crossing off as you do them. It gives you a clear guide of the next step you need to take.