New habits are hard. The best way to make them stick? Start slow, says “Atomic Habits” author James Clear. He recommends a two-step approach: Establish the baseline of your desired behavior, then build on it. “You have to standardize before you can optimize,” he tells The Post.

Forget flailing through a 10K right now. “You’re still mastering the art of showing up,” Clear says. “You only have the chance to be the kind of person who works out four days a week if you’re there in the first place. Make that the norm in your life. Once you show up, you have choices. Any running is a bonus.”

Going cold turkey on your favorite greasy takeout could torpedo early efforts to eat better, says clinical and nutritional psychologist Amanda Baten. “I like to talk about adding instead of taking away,” she says. “Start by incorporating homemade veggies into your meals. It’s a minor change that provides progress, and that’s what creates momentum.”

“This is part of something I call the two-minute rule,” says Clear. “When you’re adopting a new habit, it often helps to scale it down to just the first couple of minutes. We’re always told to start small, but it can still be easy to start too big and lose motivation.”

Amassing a fortune is a lofty goal that Baten likens to the peak of a mountain. “It’s overwhelming for anyone to think, ‘How the heck am I going to get to the top of the mountain?’ ” she says. “So what we’re looking for are the smaller steps that get us to the foothills.” A simple spending speed bump is just enough to get you going.