If you're stressed out, hungry, got the low-blood sugar, tired, distracted, etc. your attention is much less valuable (to you) than if you're relaxed, well-fed and -rested, focused, etc.

One of the greatest forms of "leverage" we have in the world is the capability of developing and focusing the quality of our attention, "concentration" or "one-point mind". That's why meditation is worthwhile (one of the reasons anyway) because, paradoxically, sitting and doing "nothing" for an hour makes the other 10~12 hours way more productive, due to the improvement in Q-of-A[ttention].