Take (one's) eye off the ball phrase
To not or unable to pay close attention to what one is doing at the time.
I set out a goal to graduate in only three years, but I took my eye off the ball, and it took me four years to complete my tertiary education program.
You are always taking your eye off the ball! That's why you haven't succeeded in business.
Luckily, as soon as I had taken my eye off the ball, my friend reminded me of my goal, and I became focused again.
To daydream
To pay your full attention to something you are doing
The verb "take" must be conjugated according to its tense.
The origin of this phrase is not clear.
If someone has a cast iron stomach, they have a strong stomach that can digest unusual food and even bad food without being ill.
Jimmy must have a cast-iron stomach, when he drank milk with lime juice and felt perfectly fine afterward.