Derek Sall, 31, still remembers the first time he realized he was in debt — and the spike of motivation he felt to pay it off.
Sall's then-wife had returned to their house from the mailbox carrying their first student loan bill. It caught the young couple completely off guard.
"I think that happens to so many people: It's six months after you graduate, you're not thinking about it," Sall explains to CNBC. "I was sitting at the computer, doing our budget, realizing we were going backwards already."
From there, Sall, who chronicles his financial journey on his blog, Life and My Finances, resolved to get out of debt as quickly as possible. Between his wife's $12,000 in student loans, his own $6,000 worth of loans, and some outstanding credit card payments, the couple carried about $20,000 worth of debt between them.
They began aggressively attacking it, and managed to pay everything back in full within 14 months.
A few years later, Sall, then 27, found himself underwater again.
He and his wife had divorced, splitting their assets down the middle. Because Sall wanted to keep the house, he ended up owing his ex $21,000. He also had $60,000 left on their $75,000 mortgage to pay.
This time, anger fueled him. Frustrated and hurt, he started by paying back his ex-wife and continued from there.
"From that point, I paid that [$21,000] off in just six months, and I paid that off so fast that I thought, 'You know what? I hate this debt, it's always keeping me down, it's always chaining me, so let's just get rid of the house mortgage,'" he says.
In another year, Sall had paid off the house and was completely debt-free again.
All told, he paid back $116,000 in debt before turning 30.
His ability to pay off debt quickly didn't stem from a high-profile job or a windfall. Rather, he focused on two things: Earning as much as possible and spending as little as possible. "At the time, [my mindset] was live on as little as possible and take on as many jobs as I can, both side gigs as well as my full-time job," he says.
A financial analyst by trade, Sall earned just $33,000 annually starting out. To supplement his income, Sall cultivated as many side gigs as he could manage, including mowing lawns, writing articles and flipping cars.
"My dad was a car dealer, so I knew a lot about cars and what they were worth," he says. "I would do it all legitimately."
Sall would buy cars in his own name to drive for a couple of months, make small updates such as replacing broken handles, and later sell them for a profit, netting around $1,000 per vehicle.
Sall also focused on building up a $1,000 emergency fund, which served as a type of financial cushion for him.
That money provided a buffer than allowed him to negotiate higher insurance deductibles. When he got down to less than 20 percent of his mortgage left to pay off, he also took his money out of escrow to avoid paying extra fees and negotiated his insurance rates down even further.
To stay motivated and on track to pay back his debt as quickly as possible, Sall utilized the snowball method, which targets the smallest debts first.
Although mathematically it makes the most sense to pay back the debts with the highest interest rates first, for Sall, starting with the smallest ones — regardless of interest rate — was far more motivating.
"It's emotion that got you into the debt, so it's emotion that's going to get you out," he explains. "You want to pay off your smallest debt and have those victories, so it's a motion to pay off the next one, and the next one, and the next one."
Sall has experts on his side. Researchers for the Harvard Business Review find the snowball method to be the most effective way to pay off debt because you're more likely to stay motivated if you can see your debts disappearing.
"Focusing on paying down the account with the smallest balance tends to have the most powerful effect on people's sense of progress — and therefore their motivation to continue paying down their debts," Remi Trudel, one of the researchers, writes for HBR.
For Sall, it was all about finding his "why."
"If you don't have your reason why, it's just not going to happen," he says. "You can say, 'Maybe I want to tackle my debt today and get started,' but you really have to have that gut fueled-emotion to drive you forward."
Between his full-time finance job, blog and side hustles, Sall still makes less than $100,000 per year. But now remarried and the father to a young daughter, Sall says he doesn't need a six-figure salary. Simply paying off the debt has allowed him the freedom to enjoy his life.
Now, he has options.
"We do tons of stuff," he says, describing life with his family. "Yesterday, we spontaneously went to a baseball game. We spent a decent amount of money, but we didn't have to think about it. I didn't come home thinking, 'Oh man, how much did we spend?' and 'What's left in our account? Are we going to make the bills this month?' It's just having that big emergency fund, that cushion."
"It's so freeing," he says.
Don't miss: Self-made millionaire recommends 5 books to help you start and master investing