#5 It's not personal -- It's strictly business
Funnily enough, although most may credit the famous line -- It's not personal; it's strictly business -- to the classic movies from The Godfather franchise; a rather shining example of the same in recent memory is when UFC megastar Conor McGregor mouthed a similar phrase to his arch-rival Khabib Nurmagomedov during their UFC Lightweight Title fight!
It's only business. Kevin Nash is a man of business, and a true master at the art of not allowing his personal differences with a business associate or rival get in the way of his work. Nash worked for several pro-wrestling organizations including WCW (1990-93 and 1996-2001), WWE (1993-96, 2002-04 and from 2011 to the present day), as well as Impact Wrestling (2004-11).
Despite having several creative differences as well as legitimate personal rivalries with fellow industry veterans such as Chris Jericho, Goldberg and a few others; Nash has always been a consummate professional -- working with whoever is put in front of him. On the other hand, CM Punk who had for long complained about part-timers being given prominent spots at WrestleMania, eventually went on to fight on the PPV section of UFC 203 and UFC 225, thereby taking up the spot which could've easily seen a better-trained fighter be featured in it.
Honestly speaking, Nash knows how to brush aside personal differences so as to get the job done, whereas Punk is yet to go of the grudge he holds against the WWE...