Washington (CNN) Republican senators left Washington for the annual August recess last week, devoid of the kind of monumental accomplishments many of them had hoped for.

"It's not good enough. We've got to do better," said Sen. Ron Johnson, a Republican from Wisconsin, of the Senate's effort so far this year.

In part, they have themselves to blame. After using a process that required only Republican support, they still failed to find consensus on a plan to overhaul the Affordable Care Act and haven't otherwise moved on President Donald Trump's legislative agenda.

Sen. Ted Cruz, R-Texas, said Republicans have four priorities: health care, tax reform, regulatory reform, and confirming conservative justices to the Supreme Court.

"If we deliver on those four, this could be the most productive congress in decades," he told reporters. "If we fail on those four, this Congress would be a heartbreaking missed opportunity."

But Republican senators have also been distracted from following through on legislative accomplishments. They worked closely with the White House and even changed Senate rules to get Justice Neil Gorsuch confirmed, but the relationship with the White House has often been sour.

"Republican Senate must get rid of 60 vote NOW!" Trump tweeted late last month . "It is killing the R Party, allows 8 Dems to control country. 200 Bills sit in Senate. A JOKE!"

Staffing kerfuffles at the White House, continued leaks about the ongoing Russia investigation and Trump's own evolving goal posts on health care all have all created an environment where senators' are slowly realizing if they want to pass a comprehensive legislative agenda, they may have to be more self-reliant.

"We're getting used to each other," said South Dakota Sen. John Thune, a member of leadership. "A lot of our members have never had a Republican administration. This is a President, obviously, who's never had to work with Congress. I just think there are some growing pains that come with that, but things we can work through. "

When Congress returns in September, they'll have a full agenda. They'll have to raise the debt ceiling, keep the government funded and renew the country's flood insurance program. They'll also have to return to work on stabilizing the health care system something most lawmakers acknowledge now requires Democratic help. And, lawmakers are expected to turn again to try and get Trump a win on tax reform.

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A Republican President, but then what?

After years of waiting for a Republican to enter the White House, GOP senators admit that they are adjusting to the fact that the conservative legislative agenda is in their hands.

"I think we're conducting our business in the way things were intended to be," said Sen. Bob Corker of Tennessee, the chairman of the Senate Foreign Relations Committee. "Look, we're separate but equal branch, and I think we understand it's up to us to pass laws and make changes and to deal with things like tax reform. "

Asked if he felt like Congress was on its own, Corker said he was relishing the freedom and urged his colleagues to accept it as a silver lining.

"Honestly I enjoy the fact that Congress, the Senate in particular, is charting a course and developing legislation and, let's face it, leading on all of these issues," Corker said. "When my members in the committee say, 'Well, we have no one here from the administration to weigh in on this,' I say, 'Be careful what you ask for. It's pretty nice the way things are.'"

Republican senators are even defying Trump in some obvious ways. After Trump suggested in a New York Times interview and Twitter that he was displeased with Attorney General Jeff Sessions, Republicans on Capitol Hill came to Sessions's defense.

Sen. Chuck Grassley, a Republican from Iowa and the top Republican on the Judiciary Committee, tweeted that the Judiciary Committee wouldn't approve another attorney general in 2017. And South Carolina Republican Sen. Lindsay Graham declared there would be "holy hell" to pay if Sessions was fired.

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'It's important to speak up'

Sens. Lisa Murkowski of Alaska and Susan Collins of Maine -- who both voted against the GOP health care bill -- said that Congress is growing increasingly more comfortable speaking up

"I don't think that the caucus is ignoring the President," Collins said in an interview with CNN's Dana Bash last week. "But there may be some ignoring of his rhetoric, which, at times, is over the top."

Murkowski agreed, saying that when the rhetoric from the Oval Office "is not constructive to governing," it's "important to speak up."

"And I think you are starting to see a little bit of that," she added.

If anything, it's been a learning curve for all sides. After a raucous health care debate and the passage of a bipartisan Russia sanctions bill that the President finally signed, Sen. Jeff Flake, a Republican from Arizona, said Trump might have learned more about how Congress operates.

"We'll stand up for our prerogatives," Flake said. "No president should expect any senator or member of the House to be a rubber stamp. We have our own franchise."