Make as Few Pawn Moves As Possible

Chess Question:
Why would black be losing if he moved Kd1.

Coach’s Hint:
Look for white moves that attack the Black
King on d8. Once you find the correct move,
check CPR to see how black would respond
to this threat.

Why should we avoid moving the same
piece twice in the opening?:

The sin of moving the same piece twice in
the opening with Ng5 lets your opponent
get more of his pieces out. Notice that
Morphy was black but because of the
disregard of this principle black is able to get
more pieces out faster.