Question

I made another earth shaking decision

Answer 1

Answer:

the decision was that he would grow a thin moustache to look handsome

Answer 2

Answer:

earth-shaking decision: something very important.

He appreciated himself and said that he had an attractive smile. Another thing that he decided was that he would always keep smiling, because he looked better when he smiled.  The doctor was being ironic when he said that ‘to keep smiling’ was an earth – shaking decision.