What common phrase is represented by the below lines

Easy going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Medium going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Tough going:
Weak, 'I can't do it, I'm staying!'
Tough, 'Let's get going.'

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

What work can one never finish?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

Can you replace the X (both small and big x) with the numbers between 1 to 19 such that all the rows of 3 numbers between X (big x) sum to 23?

What Adam and Eve do not have but the rest of the people have?

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

A girl has as many brothers as sisters, but each brother has only half as many brothers as sisters. How many brothers and sisters are there in the family?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?