Although any time is a good time to form a good habit, the start of the year is a common time to do so. With the start of a new year, it’s natural to consider if there’s anything you want to stop doing or start doing. Are there any new habits you want to forge or old ones you want to break?

In making this decision, it’s worth knowing that not all habits are the same. Although there may be plenty of good ones to choose from, some have a unique ability to have an outsized impact on your life. You start by focusing on a single habit, but soon notice positive changes in other areas as well. In The Power of Habit, Charles Duhigg labels these kinds of habits as “keystone” habits.

Physical exercise, for instance, is a classic example. Duhigg notes how studies have shown that implementing an exercise routine often correlates with other positive outcomes. Exercise may not directly cause an improvement in people’s moods, productivity, and stress management, but for some reason, that’s often what happens.

Now, since everyone’s different, your “keystone” habits will vary from someone else’s. For me, I’ve found a morning walk to have a positive impact beyond the time allotted to it. The same goes for daily setting aside time for reading and writing.

Groups can also have keystone habits. A family may have dinner together most nights, parents may have a bedtime routine with their kids, you may choose to meeting up with friends on a weekly basis. But whatever the rhythms look like, they end up having a wide-ranging, and long-lasting, impact.

Although the particular keystone habits for each person, couple, family, or larger group may differ, there is a common theme. A keystone habit provides a catalyst or foundation for other positive changes. It exerts influence on areas beyond itself.

So if you’re ever considering starting or reinforcing a habit, keep an eye out for practices that may act as keystones in your life. Perhaps you already have some in place. If so, continue to invest in them. Or perhaps none come to mind. If that’s the case, it’s never too late to explore.