In all seriousness referring must be the hardest job on earth.
It doesn't have to be. I refereed high-level HS soccer and hockey refs have told me that they think soccer is harder to ref than hockey. Hockey is faster, but the pitch is huge in soccer.
The hardest thing is having the courage to make the correct call. My advanced course was taught by a FIFA referee who said that, "The referee will always affect the outcome of the game. You can do it in a negative way by NOT making the call(s) or in a positive way by making the correct call(s)."
The 2010 FIFA WC was decided by two mistakes by a linesman in the Spain QF. Spain lost on the pitch 0-1, but won on the scoreboard because of two blown calls for offside.
Hockey refs screw up by not having the courage to make the correct calls, mostly by "managing" the game and not refereeing it. You must referee the game, NOT the scoreboard.
An example, walking off at halftime, a player said to me, "You're cheating us, ref; you called 3/4 of the fouls against us." I said, "That's because your team committed 3/4 of the fouls."
What NHL referee would have the courage to call 3/4 of the penalties against one team?
If I ran the NHL, the first thing I would do is hire someone from FIFA to run the referee program. Why? To completely change the culture of officiating.
