Success is a subjective notion, if there ever was one. But for simplicity's sake, let's assume the higher you are on Maslow's hierarchy of needs, the better you're doing. In case you don't remember the levels from Psych 101, essentially, people can't be their best possible selves (self-actualization) until lower-level needs are met first. In other words, you can't be an ideal version of yourself if you don't have enough food and money to pay the bills, or enough love and esteem to feel good about your value as a human being. So, what can you do to move yourself up the pyramid?

Check out the findings from several studies, which shine a light on what it takes to achieve more in life.

Increase your confidence by taking action.

Katty Kay and Claire Shipman, authors of The Confidence Code, wrote a stellar article for The Atlantic on this subject. Highlighting scads of studies that have found that a wide confidence gap exists between the sexes, they point out that success is just as dependent on confidence as it is on competence. Their conclusion? Low confidence results in inaction. "[T]aking action bolsters one's belief in one's ability to succeed," they write. "So confidence accumulates--through hard work, through success, and even through failure."

Broaden your definition of authenticity.

Authenticity is a much sought-after leadership trait, with the prevailing idea being that the best leaders are those who self-disclose, are true to themselves, and who make decisions based on their values. Yet in a recent Harvard Business Review article titled "The Authenticity Paradox," Insead professor Herminia Ibarra discusses interesting research on the subject and tells the cautionary tale of a newly promoted general manager who admitted to subordinates that she felt scared in her expanded role, asking them to help her succeed. "Her candor backfired," Ibarra writes. "She lost credibility with people who wanted and needed a confident leader to take charge." So know this: Play-acting to emulate the qualities of successful leaders doesn't make you a fake. It merely means you're a work in progress.

Improve your social skills.

According to research conducted by University of California Santa Barbara economist Catherine Weinberger, the most successful business people excel in both cognitive ability and social skills, something that hasn't always been true. She crunched data linking adolescent skills in 1972 and 1992 with adult outcomes, and found that in 1980, having both skills didn't correlate with better success, whereas today the combination does. "The people who are both smart and socially adept earn more in today's work force than similarly endowed workers in 1980," she says.

Train yourself to delay gratification.

The classic Marshmallow Experiment of 1972 involved placing a marshmallow in front of a young child, with the promise of a second marshmallow if he or she could refrain from eating the squishy blob while a researcher stepped out of the room for 15 minutes. Follow-up studies over the next 40 years found that the children who were able to resist the temptation to eat the marshmallow grew up to be people with better social skills, higher test scores, and lower incidence of substance abuse. They also turned out to be less obese and better able to deal with stress. But how to improve your ability to delay things like eating junk food when healthy alternatives aren't available, or to remain on the treadmill when you'd rather just stop?

Writer James Clear suggests starting small, choosing one thing to improve incrementally every day, and committing to not pushing off things that take less than two minutes to do, such as washing the dishes after a meal or eating a piece of fruit to work toward the goal of eating healthier. Committing to doing something every single day works too. "Top performers in every field--athletes, musicians, CEOs, artists--they are all more consistent than their peers," he writes. "They show up and deliver day after day while everyone else gets bogged down with the urgencies of daily life and fights a constant battle between procrastination and motivation."

Demonstrate passion and perseverance for long-term goals.

Psychologist Angela Duckworth has spent years studying kids and adults, and found that one characteristic is a significant predictor of success: grit. "Grit is having stamina. Grit is sticking with your future, day in, day out, not just for the week, not just for the month, but for years, and working really hard to make that future a reality," she said in a TED talk on the subject. "Grit is living life like it's a marathon, not a sprint."