In 2014, David Cahill, 30, graduated with a master's degree in school leadership. His diploma came with a tab for nearly $20,000. When he entered his repayment period that November and opened his first statement, it "revealed that a 10 year repayment plan would cost a total of $27,178.23," he writes on his blog, FinanceSuperhero. "In that moment, I was determined to ensure that my $18,000 educational investment would not become a $27,000 one!" What's more, the Chicago-based millennial owed more than $5,000 on his undergrad student loans. "I couldn't help but realize that I had taken on way more than I could handle," Cahill tells CNBC.

David and Meg Cahill Courtesy of David and Meg Cahill

By February 2016, he and his wife Meg, 28, had wiped out his undergrad loans and started to make a dent in his grad school loans. But Cahill still owed nearly $18,000. That's when the couple buckled down, Cahill tells CNBC: "We realized that this debt was out of control. The weight of the monthly payments was causing enormous stress and unhappiness, so we decided to really push things into high gear and turn that emotion into action." By April 2016, 54 days after committing to tackling the remaining debt, the Cahills were completely debt free, thanks to extreme saving and a decision to dip into their robust emergency fund. Here's how they did it:

They decided, "Sacrifice now ... win later"

Upon reviewing their monthly expenses, "we realized that we were going out to restaurants and drinks with friends far more often than was practical," Cahill tells CNBC. "Everybody says it, but we were wasting a lot of money at Starbucks and Dunkin' Donuts. We were regularly going to movies, buying a lot of non-basic grocery items and probably the biggest thing was that we had some unused subscriptions and memberships." Their mantra became, "Sacrifice now in order to be able to win later." They pressed pause on pretty much all spending that wasn't for necessities. "During those months, we paid our mortgage, utilities, required minimum payments. And we bought basic groceries. That's it," Cahill writes. By reducing their spending to about $3,200 a month, they were able to save $7,800 in just 54 days, all of which went towards paying down the loans.

They saved more than half their income

Generating two incomes and living on the smaller one while banking the other is a popular money saving strategy among early retirees. It worked for the Cahills, who decided to live off of Meg's $40,000 teaching salary and direct David's $62,000 school administrator salary exclusively towards paying down the student loans. "The majority of Meg's earnings were the earnings that were keeping us afloat, while almost all of my paycheck was going towards the debt payoff," Cahill says. That meant they were setting aside more than half of their combined income.

The Cahills live in the suburbs of Chicago Courtesy of David and Meg Cahill

They got their friends on board

As soon as the couple committed to paying off their loans aggressively, they sat down with their friends, explained their ambitious plan and asked them to provide accountability. It was the smartest move they made during their debt repayment journey, Cahill says: "The support that we got from them — the texts and phone calls of encouragement — really made a difficult experience for us that much more gratifying. "Accountability was a huge piece for us and we were fortunate to have good friends that provided that."

They put their other financial goals on hold

The couple decided to focus exclusively on paying down the debt, which meant making bigger sacrifices than skipping Starbucks and canceling a gym membership. They stopped investing, other than their required pension contributions, and took a large chunk out of their emergency fund to make the final payment, Cahill tells CNBC: "Around day 45, we realized that our emergency fund was out of balance with what we really needed. We decided to make a big push and raid our emergency fund, and that gave us the final little boost we needed. In April 2016, the couple took about $10,000 out of their emergency fund in order to make their last payment. They made sure to leave one month's worth of living expenses in the fund, and now that they're out of the red, "we're working on building it back up to six months' worth again," Cahill says.

David and Meg Cahill Courtesy of David and Meg Cahill