The luster of autumn has faded, and the harsh reality of winter has set in. And so has your seasonal depression. How cruel it is! to trade memories of the pumpkin patch, watercolor forests, sunset bonfires in cozy sweaters, for mountains of dirt-blackened snow piled up outside your window, neighbors turning to strangers under heavy winter wear and a mere eight hours of weak sunlight per day.

During the winter months in most of the U.S., it can be hard to fight off depressive episodes, negative feelings and cold-weather malaise, but it’s not just the frigid temperatures and social isolation that result in declining mental health, there’s a science behind it, too. According to Psychology Today, shorter days and limited sunshine interrupt our circadian rhythm, which results in metabolic changes that affect well-being. Two neurotransmitters are at the center of your lousy mood: decreased serotonin and increased melatonin in the body cause feelings of sleepiness, irritability and sadness.

Left unchecked, the dead of winter could see you isolated, depressed and without an ounce of strength or motivation to fight through the dark. But it is possible to stay on top of these dark feelings. “A lot of people don’t realize there are baby steps and small little things we can do to get those neurotransmitters [going] that starts to change all of our body chemistry,” says Peggy Sullivan, leadership speaker, “happiness expert” and founder of the nonprofit for women SheCAN!. “And that, to me, is all about self-care.”

Sullivan refers to “microsteps” that anyone can take to increase feelings of well-being and happiness, which becomes especially important during winter months. “Happiness is a muscle, and the more you flex it, the stronger it gets, the more capable it gets,” Sullivan says, noting that even small changes in daily life — these microsteps — that bring joy compound to enforce overall well-being. “We tend to think that happiness is something that happens to us, [that] we crash into it, but happiness is a choice,” she says.

Sullivan didn’t come to this realization easily — when she was very young, her mother was diagnosed with pancreatic cancer. “She was in a state of depression and sadness and frustration and anger that was pretty intense,” Sullivan says. But one day, Sullivan walked into the hospital room and her mother was smiling while enjoying a hot fudge sundae and listening to music — acting in a way she hadn’t for a very long time. “I thought, my god, what a big change … and she said, ‘You know, I just got the big secret to life: Happiness is my responsibility,’” Sullivan remembers. In her final weeks, her mother made every attempt to trade anger for joy. “Life is hard, life is challenging; we need to acknowledge the challenges,” Sullivan says. “But attitude is so contagious, and happiness is contagious. If you watch somebody who’s happy enter the room, the whole room lights up.”

Of course, maintaining a happy mood can be easier said than done, especially during the colder months. Busy schedules juggling responsibilities related to work, friends and family, and the home also don’t leave much room to focus on yourself and your happiness. Through SheCAN!, Sullivan hosts more than 80 speaking events every year; she notes that most of the crowds she speaks to consider themselves extremely busy — “But being busy doesn’t necessarily mean they’re happy and fulfilled,” she says.

That’s why Sullivan is such a steadfast proponent of self-care. She notes that improved mood and sustainable happiness can reduce anxiety while actually increasing energy and productivity. It all comes back to the “science” of happiness — “One of the easiest ways to release endorphins is through self-care,” Sullivan says. And this is where those microsteps come into play. “Those tiny little happiness rituals, those small things you can do that bring joy to you, even if it’s for a fleeting second, [will get] the endorphins going,” Sullivan says.