If you have a large task to complete and it doesn’t easily break into components, make it a daily habit.
My digital photo catalog contains 68,255 images right now. Some are tagged and evaluated, many are not. I have created a habit of working a little on cleaning up my photo collection every day. That means I feel I’m progressing towards my goal of having everything organized, even though there is still a long way to go.
For me, it works to have a habit-tracking app that reminds me not to “break the chain” every evening if I haven’t gotten around to a little photo sorting during the day. But you can also establish a habit by piggybacking it onto something you already do.
The difference between feeling in control and feeling overwhelmed by large tasks is whether you are moving towards your goal or are standing still. Move.