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 am white when I am dirty, and black when I am clean. What am I?

What Time Should the last watch show in the below figure?

Can you find the missing piece of the Porsche?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

I am quite hot but become too cold if you remove the first two letters. What am I?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

Find the number of squares in the below picture

In Greek mythology, the Sphinx sat outside of Thebes and asked this riddle of all travellers who passed by. If the traveller failed to solve the riddle, then the Sphinx killed him/her. And if the traveller answered the riddle correctly, then the Sphinx would destroy herself. The riddle:

What goes on four legs in the morning, on two legs at noon, and on three legs in the evening?

Oedipus solved the riddle, and the Sphinx destroyed herself.

Can it be possible to build a house that has all its four walls facing towards the South?