The Greek philosopher Aristotle said it first and best: “Good habits formed in youth make all the difference.”

But it's tough to know at age 15 that your hunched posture while texting may cause you chronic neck pain when you're 40, or that living on diet soda and doughnuts in college can contribute to heart disease.

The truth is that the seeds of your future health are planted early.

But there’s good news: You can reshape your future — and have fun doing it. Here’s how:

Weight management. Three simple guidelines that will transform your health.

• No sweetened beverages. Limit 100 percent natural juices (nothing added) to 4 ounces a day.

• No fried foods.

• Eat a salad or a pile of veggies at every meal. Have two pieces of fruit or servings of berries daily.

Sleep. Kids ages 6-13 need nine to 10 hours; aim for eight to 10 hours if you are 14-17; seven to nine hours if you are 18-25.

Physical activity. A 2018 study found that at age 19 most Americans are as sedentary as a 60-year-old (who shouldn't be sedentary either). Screen time is a brain killer and a heart danger, and too much social media time raises your risk for depression. Aim to get out and about as part of a sports team, take a jog with a pal, go to a spin class, or go for a bike ride. Your minimum goal: 60 minutes of aerobic activity a day. And more is better.

Stress management. Between school pressures, social anxieties, conflict with parents, and worry about the future, many teens report feeling daily stress. Regular physical activity helps dispel an amped-up stress response. Talking with friends, a favorite teacher or counselor, or parents and siblings can help. So can declaring digital holidays.