In Poker a Jack is as good or better than about 3/4 (OK 76.92%) of the cards in the deck, losing only to Queen, King, and Ace. So a “Jack of all Trades” is good at many things. The full verse is
“Jack of all trades, master of none,
though ofttimes better than master of one.“
Scott Adams offered “Career Advice” in July of 2007:
But if you want something extraordinary, you have two paths:
Become the best at one specific thing.
Become very good (top 25%) at two or more things.
The first strategy is difficult to the point of near impossibility.