There are the bumps and bruises from training. And constantly watching what you eat to ensure you make weight. But worst of all is the time away from family.
"For me it's like a job," said the Montreal bantamweight, a father of two. "Training two times a day.
"Right now I train at night. So my kids, my wife, we take time to eat together, play for one hour together. Then Papa has to go do jiu-jtsu. And my kids say 'Again, Papa? Why? Why jiu-jitsu?'
"I say 'It's my work. I come back, I come back early.' But sometimes I come back and they're sleeping. The last two months is like that."
His son is three and daughter four. All they know is that Papa is not there.
Menjivar (24-8) looks to reap the rewards of that sacrifice Saturday night when he meets highly touted American Mike (The Hulk) Easton (12-1) on the undercard of UFC 148 in Las Vegas. Middleweight champion Anderson Silva faces Chael Sonnen in a grudge rematch in the main event at the MGM Grand Garden Arena.
The Menjivar-Easton fight is the first on the high-profile main pay-per-view card.
Tito (The People's Champion) Ortiz, in his swan song, and Forrest Griffin face off in the co-main event in a rubber match between former light-heavyweight champions. Montreal middleweight Patrick (The Predator) Cote is also on the main card, returning to the UFC to face former Strikeforce title-holder Cung Le.
Family is important to the 30-year-old Menjivar, who did not fight between November 2006 and June 2010. He never stopped training but put his fighting career on hold due to knee surgery and the birth of his kids.
Menjivar's day job was working in airport security, a position he kept until he was laid off last fall when the contract went to a new company. Menjivar had spent five years on the job.
Now he focuses full-time on training and fighting.
Since returning to the cage, he has won four of five fights. He lost to Brad (One Punch) Pickett in his lone WEC fight in December 2010 but is 3-0 in the UFC with wins over Charlie Valencia, Nick Pace and John Albert. Menjivar collected US$50,000 for submission of the night in stopping Albert, a graduate of Season 14 of "The Ultimate Fighter" reality TV show, in February.
While booked to fight on UFC 148, Menjivar found himself caught up in the turmoil surrounding injury-plagued UFC 149 card July 21 in Calgary.
Menjivar was originally slated to face Renan Barao in Las Vegas. But the rising Brazilian star was shifted mid-May to the Calgary card to fill in for injured featherweight champion Dominick Cruz against Urijah Faber.
Menjivar says the UFC told him it was looking at him, Barao and another fighter — possibly Michael (Mayday) McDonald — as opponents for Faber for the interim featherweight title. Menjivar and Faber first met in 2006 when the Canadian was disqualified for an illegal kick to a downed opponent on a TKO card.
The announcement was made on live TV during an episode of "The Ultimate Fighter," with Menjivar suspecting it was not going to be him because he did not get a call in the days leading up to the show.
Faber said later that UFC president Dana White had misled him by telling him he would be fighting Menjivar, when all the time he had Barao waiting in the wings to up the surprise factor.
Menjivar didn't seem to mind. He just turned his attention to Easton.
"Everybody's happy," said the five-foot-six 135-pounder. "I have a fight, Barao has a fight."
Easton, who trains with Cruz, can beat you up and then work out the kinks. He's a black belt in Brazilian jiu-jitsu who went to massage therapy school.
The 28-year-old is 2-0 in the UFC with wins over Byron Bloodworth and Jared Papazian. Easton is currently riding a seven-fight win streak and has not lost since a TKO at the hands of Reynaldo Walter Duarte in September 2007.
He was due to fight Montreal's Yves Jabouin in May but had to withdraw due to injury. In the intertwined world of MMA matchmaking, Easton was replaced by Jeff (Hellbound) Houghland who was due to face Barao at UFC 148. His move opened the door for Menjivar to take on Barao, a least for a while on paper.
"It's part of the sport. It's normal," Menjivar said of the snakes and ladder matchmaking.
Over his 11-year MMA career, Menjivar has fought from 135 to 170 pounds. His resume includes fights with Georges St-Pierre, Bart Palaszewski, Caol Uno, Faber, Joe Lauzon, Vitor Ribeiro, Jeff Curran, and Jason Black in non-UFC or WEC bouts.
The 2002 St-Pierre fight was the first of the future UFC champion's pro career and the fifth fight (and first loss) for Menjivar.
Years later, St-Pierre and Menjivar share the same coach in Firas Zahabi. And Menjivar is enjoying a new lease on life in the cage with the UFC having opened its door to the lighter weight classes.
"For me it's like a second chance in the UFC," he said. "A second career in MMA after a (knee) operation. Everything's good for the moment.
"Enjoy the moment. ... No regrets after."
Menjivar, who came to Canada with his family from El Salvador when he was 11, says he is not sure what awaits him after this fight in terms of the UFC.
But he has some family time to catch up on.
"I promised them (his kids) we'd see family, go to the beach and play, play, play."
Whatever the outcome Saturday, Menjivar has something to look forward to.
"If I win, I'm happy. I go back home and play with my kids. If I lose, I'm happy. I go back home and play with my kids. What's the difference?"