A lot of us have been in a job we know we should quit, but just don’t. It takes a big event or getting fired.
in an interview with CNN’s Jake Tapper on “State of the Union” in late May, Rubio allowed that he would have “maybe” considered reconsidering his planned departure. But, he said, “I have a real good friend I’ve known for a long time who I was running for the Senate with. I didn’t run. I said I wasn’t going to. He got into the race.” https://www.cnn.com/2016/06/22/politics/marco-rubio-running-again-does-not-like-senate/index.html
“I’ve always said it, from the very beginning of this race, I’m going to go out and be who I am, and if that’s enough to be president, then I look forward to serving the country,” Rubio told the Miami Herald on the eve of his exit from the GOP primary.
“And if it isn’t, then I have other things I want to do in my life,” he said. “You know, public service is what I do. It isn’t who I am.”
He added, “We’re not going to fix America with senators and congressmen.”
“I went to the U.S. Senate because I didn’t like the direction of this country and I didn’t think either party was doing a good job in that regard,” he continued. “And that’s the same reason why I’m not running for re-election.” Fox (Hannity) broken link
“That’s why I’m missing votes. Because I am leaving the Senate.”
“If I decide the best place for me to serve America is to run for president, that’s what I’m going to do,” he told South Florida’s Sun-Sentinel in February 2015.
“And I’m not going to have an exit strategy premised on the idea that I’m going to pivot back to a Senate race. We have quality candidates in the state on the Republican side who could run and make great senators.”
Rubio has rarely shared a kind word about his current and, now, potentially future day job.
As early as December 2011, less than a year after taking office, the first-term senator was already frustrated by congressional gridlock.
“I can’t think of a single real high point,” Rubio said in an interview with the Sun-Sentinel.
“It seems like the entire year has just been one big staged event, trying to get political advantage in the next election,” he added. “You look at the major issues facing this country, and few, if any of them, have been confronted.”
Washington post similar article not great: https://www.washingtonpost.com/politics/2015/10/25/28cfaff0-6d59-11e5-9bfe-e59f5e244f92_story.html
Real Woman's Health 
Where I used to work … there were a couple of people in relatively high up positions in the organization. They were both hard-core conservative Republicans who hated government, hated government employees, hated it all. But they had both spent their lives working for … government. I’ve got to believe they have a lot of self-hate locked up inside of them. Kind of like Rubio and many right-wingers who have run for office to occupy a spot they claim to hate.