One of my favorite metaphors for maximizing productivity is filling a bucket with water, sand, gravel, and rocks.
You can get the most in the bucket if you put the rocks in first, then the gravel, then sand, and finally the water.
The meaning of the metaphor in terms of productivity is to schedule the big important tasks first. The rest of the smaller tasks will find a spot within the cracks and finally, the little everyday things (like the water) will get done without having to schedule anything at all.
Hope you like this metaphor.