“So what's their plan, hitting Sebastian over the head with Jace until he passes out?”

Jace and Clary, pg. 220
Source: The Mortal Instruments, City of Lost Souls (2012)
Context: "Stay with me. We can see the whole world."
"I am with you. I'm not going anywhere."
"Is there anything special you want to see? Paris? Budapest? The Leaning Tower of Pisa?"
Only if it falls on Sebastian's head, she thought.

October 1987 Source: “Everyone has a plan until they’ve been hit” (boxing adage) http://www.barrypopik.com/index.php/new_york_city/entry/everyone_has_a_plan_until_theyve_been_hit_boxing_adage, The Big Apple, Barry Popik, May 05, 2012 Source: " Mike Tyson explains one of his most famous quotes http://articles.sun-sentinel.com/2012-11-09/sports/sfl-mike-tyson-explains-one-of-his-most-famous-quotes-20121109_1_mike-tyson-undisputed-truth-famous-quotes", Mike Berardino, Sun Sentinel, November 9, 2012]

Often quoted as "Everybody has a plan until they get punched in the mouth." Sometimes misattributed to Joe Louis.
On boxing

The Independent, The Independent, Professor Sidney Morgenbesser: Philosopher celebrated for his withering New York Jewish humour http://www.independent.co.uk/news/obituaries/professor-sidney-morgenbesser-550224.html, 6 August 2004. Obituaries – Sidney Morgenbesser, 82, Kibitzing Philosopher, Dies http://www.nytimes.com/2004/08/04/obituaries/04morgenbesser.html. The New York Times (September 8, 2004). Some of his students then argued that it may have been unjust, because he had not been proven guilty, but it was not unfair because the others were treated in the same way. The Times, Sidney Morgenbesser: Erudite and influential American linguistic philosopher with the analytical acuity of Spinoza and the blunt wit of Groucho Marx https://www.thetimes.co.uk/article/sidney-morgenbesser-5cz8gg8qfvm, September 8, 2004. This alternative version is sometimes attributed to Morgenbesser himself.

Source: Dreams of Steel (1990), Chapter 55 (p. 405)

God Bless You, Dr. Kevorkian (1999)

Variant: You're not going," he said as soon as she'd finished. "If I have to tie you up and sit on you until this insane whim of yours passes, you are not going to Idris." - Jace
Source: City of Glass

Press conference, reported in Jacob Bogage, " ‘I wanted to hit a couple of those speakers so hard', Trump says of Democratic convention https://www.washingtonpost.com/news/morning-mix/wp/2016/07/29/i-wanted-to-hit-a-couple-of-those-speakers-so-hard-trump-says-of-dem-convention-critics/", The Washington Post (July 29, 2016).
2010s, 2016, July