The upcoming Saturday Night's Main Event will mark the end of an era, as John Cena will wrap up his legendary wrestling career. Emotions are running high and the air is filled with melancholy as The Cenation Leader prepares for one last walk down the ramp. WWE is set to host this historic moment in the Capital One Arena in Washington DC and there is no scope for mistakes.WWE's creative head, Triple H, has been on the fans' radar lately due to his contentious booking decisions. Hence, there is a growing premonition among fans that he could fumble Cena's final match. For a moment this big, there is no margin of error. There are several things that The Game must not do at SNME, which could spoil what is set to be a historic moment.Here are three mistakes WWE must avoid in John Cena's final at Saturday Night's Main Event:#3. Placing this match in the openerSaturday Night's Main Event will feature four matches and recent reports from Bryan Alverez states that John Cena vs. Gunther will open the show. However, WWE must ensure that this does not happen. The Cenation Leader's farewell match is a grand occasion that will go down in history and it deserves the biggest and brightest spotlight.Having it in the opener will be a disgraceful move, and the company must avoid it. This monumental match deserves to be in the main event of SNME, with Cena's retirement being the ultimate highlight. WWE must build the entire night centered around the 17-time World Champion and have him close the show one last time before riding off into the sunset.#2. Ending the match under ten minutesJohn Cena will wrestle his last match this Saturday and fans are hoping for it to be an incredible one. Well, the gravitas of this moment is far more than one could comprehend and so WWE must not end this match in under ten minutes. Keeping it a short match will leave an teribble impression on fans, which could potentially taint the glamor of this historic night.The company should give Cena vs. Gunther adequate time, allowing both superstars to deliver an instant classic. The Franchise Player should end his last fight after giving his absolute best, showcasing every move and maneuver he has in his arsenal one last time. It should be a great wrestling match that could keep fans on their feet every second of it.#1. Making John Cena tap out in his final matchOne of the biggest mistakes WWE must avoid in John Cena's final match is making him tap out to Gunther. For the past two decades, The Cenation Leader preached to the world to never give up, even in the face of adversity and he lived by it every moment. Therefore, Cena giving up in what will be his last match will fracture everything he built in the last 23 years.WWE must prevent such a thing from happening to protect John Cena's legacy and integrity, as he motivated an entire generation with his "Never Give Up" mantra. Even if Gunther locks him up in a submission hold, Mr. Hustle Loyalty & Respect must hustle until his last gasp and stay loyal to his words in the face of defeat before heroically passing out instead of tapping out.