Federal workers woke up to a harsh reality on Friday when they did not receive their expected paychecks for the first time as the partial government shutdown entered its 21st day.

An estimated 800,000 federal employees have been furloughed or are working without pay, throwing everything from airport security to environmental protection to federal resources for low-income housing into jeopardy.

The last government shutdown to have lasted this long was the impasse that stretched from December 1995 to January 1996, when President Bill Clinton and the GOP-controlled Congress were at loggerheads. As of Friday afternoon, with the shutdown poised to become the longest in U.S. history, President Donald Trump and Congress appeared no closer to a deal to reopen the government.

Trump on Friday continued to lambaste Democrats, including House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer, for standing firm in their refusal to fund a wall on the U.S.-Mexico border.

"Humanitarian Crisis at our Southern Border," the president said on Twitter a day after traveling to Texas to bolster his argument for the wall. "I just got back and it is a far worse situation than almost anyone would understand, an invasion!"

Humanitarian Crisis at our Southern Border. I just got back and it is a far worse situation than almost anyone would understand, an invasion! I have been there numerous times - The Democrats, Cryin’ Chuck and Nancy don’t know how bad and dangerous it is for our ENTIRE COUNTRY.... — Donald J. Trump (@realDonaldTrump) January 11, 2019

"The Steel Barrier, or Wall, should have been built by previous administrations long ago. They never got it done - I will. Without it, our Country cannot be safe. Criminals, Gangs, Human Traffickers, Drugs & so much other big trouble can easily pour in. It can be stopped cold!"

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

With negotiations at a standstill, Trump has threatened to keep key agencies shuttered for months or even a year if Democrats don't agree to allocate billions for his border wall. The president has even signaled that he would declare a national emergency to bypass Congress and siphon billions from the federal government to build the wall.

On Friday, the Democrat-controlled House passed two bills to provide relief to workers and reopen some essential federal agencies. One bill to reopen the Interior Department, the Environmental Protection Agency and other related agencies passed 240 to 179, with 10 Republicans voting with Democrats. The other bill, which guarantees back pay to federal workers, passed with overwhelming bipartisan support, 411 to 7. Seven Republicans voted against that measure.

Currently, some government agencies are relying on temporary funds to keep some operations going, but experts have warned that the situation could get grimmer if it drags on.

For many workers going without pay, it's already dire.

William Villegas and Michelle Seeley, a couple that works as contract employees for the Kennedy Space Center and members of the Association of Machinists and Aerospace Workers, told NBC News on Friday that the uncertainty has caused considerable worry in their household, especially since they have two children.

“I'm severely disappointed in the government, all of them, and I vote in every election,” Seeley said. “And as a member of the union, I've taken part in rallying other people to vote because I think it's an important part of the democratic process, so the whole thing is disappointing to me because I feel like nothing is working the way it's supposed to work in the government.”

Since both are contract employees, they are not guaranteed back pay if the government reopens. The couple said they have savings that they haven't dipped into yet, but health care expenses are a concern.

“Well, we have two small children, so the medical issue is constant,” Seeley said. “You never know when they're gonna get sick, or need something.”

Villegas said the shutdown “didn’t have to happen” and pinned some of the blame on Trump, alluding to separate instances in which either the House or the Senate passed bills that would have created a path to ending the stalemate.

U.S. Internal Revenue Services employees rally in front of the Federal Building against the ongoing U.S. federal government shutdown, in Ogden, Utah on Jan. 10, 2019. George Frey / Reuters

LeRoy and Judy Smith also had harsh words for Washington. LeRoy, also a member of the the Association of Machinists and Aerospace Workers, is an electrician at the space center. The couple said they live paycheck to paycheck, and that Judy has a condition that causes seizures, requiring her to rely on expensive prescription medication.

“He doesn't like having to say that he can't do a thing, especially when it's for me,” Judy said. “He doesn't like to say he can't get my medicine for me.”

Since the shutdown, LeRoy said he has been considering temporary work to keep “his head above water.”

"It's childish to shut down the government just because you can't come to an agreement," LeRoy said.

"It's like we're being held hostage," Judy added.

The Associated Press reported on Friday that the government shutdown has suspended federal cleanups at Superfund sites around the nation and forced the cancellation of public hearings. As a result, a mostly African-American community in Alabama, for instance, has been forced to cope with high levels of arsenic, lead and other contaminants in the soil around homes.

Low-income senior citizens in Jacksonville, Florida, have also been left to fend for themselves because the shutdown froze funds the Department of Housing and Urban Development used for low-income housing.

And more grim scenarios could happen if the shutdown continues to drag on, including 38 million low-income Americans losing access to food stamps, 2 million losing access to rental assistance and facing possible eviction and the federal court system almost screeching to a halt.