I know it's been a while but I was thinking earlier, all the great match ups for him.
Big Nog, JDS (fight that was supposed to happen, and if he loses to Reem), Cain rematch, etc.
Dude didn't like getting hit. Hard to be a fighter when you don't like getting hit. 
specifically did not like getting hit in the face.
face hit getting the didn't like in.
Honestly I don't think anyone would like getting hit with Überknees and Überkicks
Just thinking about it, sad day for MMA. He had many great fights left in him
Honestly he seemed really bummed out quitting. He said that he told his family that if he lost the fight against Reem, he would quit... kept the promise to his family.
And to be fair having his organs rearranged by doctors, then by Reem, probably had something to do with it too.
He acknowledged he couldn't be the absolute best. That Overeem and co are just better. He does not want to take "interesting fights."
"Hitting of said face, he did not like"
-Goldie
He thought MMA/the UFC was a joke. He was wrong.
Whatever the actual reason for retirement, you have to respect him for going in there and fighting guys like Overeem, Cain, Mir, and Carwin... Good lord, the beating Shane put on him that night... Anyway, hope we haven't seen the last of him, but I'm pretty sure that we have.
texuspete00 - He acknowledged he couldn't be the absolute best. That Overeem and co are just better. He does not want to take "interesting fights."
This. I hated on lesnar so much. Now I regret it and respect the man.
lesnar's ego is too big to be second best and I think he realized that he wasnt good enough. Same with his football career.
MickColins - Dude didn't like getting hit. Hard to be a fighter when you don't like getting hit.
Becuase he wasn't the same fighter as he was in 09, because of his surgeries. That Lesnar would have gone 43759575373-0 and would have been able to beat a robot, Jesus Christ and a Tornado in the one night!
What do you mean, why did he retire? He had a fucking foot of intestines surgically removed. He had nothing left to prove, and he's very wealthy. No reason to keep going.
He had a sensitive face.
If it ain't Dutch, it ain't much - Had nothing to do with being hit.Riiiiiiiiiiiiiiiiiiiiiiiiiiiiiight
Guy wanted to spend more time with his family and help raise his kids.
Nothing wrong with that.
please people my understanding was in training no one was allowed to punch him in the face while sparring what kind of sparring is that?
He has a history of quitting when he can't be the best.
Just like when he didn't want to go to Nfl Europe and earn a spot back on a pro roster
He won some good fights, became champion, but this isn't the sport for him.