Get tuned up.
Sometimes our brain does not function as we expect it to.
Yesterday I made a lot of mistakes while working. I also noticed my mistakes even after I got a task done—and threw away my work (mistakes included) as it would take too much time to redo it.
A lack of focus is inevitable. It happens no matter what we do, even when we have many things to do, and leads us to make a mistake. When it happens, all we can do—and should do—is to calm ourselves down, no matter how busy we are.
Breathe slowly, meditate, take a walk… Five-minutes break to calm you down can save hours later.