A small completed task can open psychological space for a larger one.

Finishing something, even something minor, changes your internal state. The task stops occupying attention, there is evidence that you are someone who completes things today, and the next item looks smaller from there. That is why a small completion is often the right first move when facing something large, despite feeling like avoidance.

On a day when the big thing seems impossible, finish one small thing properly and completely. Not as a substitute but as a way in. Then look at the large task again, and notice that it has usually shrunk slightly.