The easiest tasks often volunteer themselves first.

Easy tasks put themselves forward. They are visible, quick, and finishable, and they arrive with a small reward attached, while the important work is vague, difficult, and offers nothing until much later. Given a free hour, the easy things will fill it without you deciding anything.

Decide the day before what the hard thing is, and start with it before the small ones have had a chance to present themselves. Order is the intervention, not effort.