Sen. Cory Gardner (R-Colorado) has had a long week. 

After announcing Colorado (and other states') pot companies were not far away from being able to legally use the U.S. banking system, fellow Republican Sen. Chuck Grassley tanked the idea before Gardner even had a chance to talk about it. That was Tuesday.

On Wednesday, he got a little heated when talking to fellow Republican Sen. Mike Lee from Utah about his public lands bill. There were actually several bills up for debate on the same topic, but Lee tanked them all because Congress won't prevent presidents from creating National Monuments in Utah, per the Salt Lake Tribune.

Gardner was not happy.

“Let me talk about this because I’m pretty doggone upset...” he said, hitting his hand on a desk. "You wonder why people are sick of this place? It's because of tonight."

Thursday was easier on the senator. It was also the day Defense Secretary Jim Mattis announced he would step down from his position in February 2019. The White House said Mattis was retiring.

"Because you have the right to have a Secretary of Defense whose views are better aligned with yours..." Mattis' resignation letter reads. "I believe it is right for me to step down from my position."

President Donald Trump commended Mattis over Twitter. "General Jim Mattis will be retiring, with distinction, at the end of February, after having served my Administration as Secretary of Defense for the past two years."

Gardner's initial response to Mattis' resigning/retiring was jaunty. "General Mattis has served the American people honorably for decades & always put his country first," read a tweet from Gardner's official account.

"His steady leadership will be missed. I enjoyed working with General Mattis on securing US global leadership for future generations, including a free & open Indo-Pacific."

MORE | Defense Secretary Mattis retiring, Trump says

Several fellow Republican Senators issues statements seemingly at-odds with Gardner's bullish response.

Florida Sen. Marco Rubio, for example, said after Mattis' announcement that Congress must fulfill its Constitutional duty to act as oversight for the president.

"Just read Gen. Mattis resignation letter," Rubio wrote. "It makes it abundantly clear that we are headed toward a series of grave policy errors which will endanger our nation, damage our alliances & empower our adversaries."

Rubio wasn't the only one with such sentiments for the announcement. Sen. Ben Sasse (R-Nebraska) said Mattis gave Trump advice he needed to hear.

RELATED | Mattis leaving as Pentagon chief after clashes with Trump

"Isolationism is a weak strategy that will harm Americans..." the senator wrote on Twitter.

9NEWS' anchor Kyle Clark reached out to the Gardner camp about the senator's tweet. A spokesperson said, "Of course [Gardner]'s concerned" about Mattis' exit. 

Colorado's other senator, Michael Bennet (D-Colorado), issued a statement saying that both sides of the aisle viewed Mattis as a firm hand in the Trump administration. 

"His resignation letter is a poignant testament to enduring American values and alliances," Bennet said.

RELATED | Gardner gets agreement on vote for conservation-fund reauthorization

Thursday for Gardner was a sort of course correction for the week. Instead of the struggles of Tuesday and Wednesday, Gardner had a big success. As Colorado Politics reports, Gardner said Thursday that he's worked out an agreement with Senate leadership to introduce and vote on legislation next month to reauthorize the federal Land and Water Conservation Fund.

The fund expired at the end of September and the current administration did not extend it. It was created in 1964 and provides grants to protect and develop the nation's public lands (be they national, state or local). 

Gardner said at the end of November that he was "honored" to be a part of the bipartisan reauthorization effort.

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