1. Keep moving. Sedentary lifestyles are the defining physical difference between young and old. Just look at kids on a playground and see how they seem to have never-ending energy, while the older people just sit on the benches watching.

The more you move, the better your chances of staying healthy and young.

You don’t have to become a super athlete or join a gym. Just walk around your apartment, your house, your block, your neighborhood.

And while you’re at it, make friends and socialize. Being part of a community takes your mind of your aches and pains and keeps you young and involved.

2. Drink plenty of water. I cannot overemphasize the importance of staying hydrated. Most of the human body — 60 percent — is made of water. Blood is 92 percent water. The brain and muscles are 75 percent water. Bones are about 22 percent water. A human can survive for a month or more without eating food, but only a week or so without drinking water.

When patients tell me they don’t drink water because they don’t like the taste of it, I explain that it’s not about taste, it’s about survival.

Water flushes out impurities and toxins and gets rid of the viruses that attack us all day long. So drink as much as you can — the more the better. A healthy person cannot drink too much water because our kidneys are fine-tuned to get rid of every drop of unnecessary water.

3. Have an active sex life. Having sex with your partner is great emotionally and physically. The problem with sex is that while it is great for you, it gets boring. Year after year with the same partner in the same circumstances can get tedious. But because it is healthy, you need to focus on how to make it exciting and make it last.

First, keep your hormones in balance. Stop drinking too much, stop eating too much, and become more romantic.

Women find men sexy under the most unlikely of circumstances.

When a man helps around the house, helps with the kids or grandkids, pays attention to the dog, and is kind and pays compliments to his partner after decades of togetherness, his partner will find him very sexy. And most women will certainly go the extra mile to make it happen.

Don’t expect sex if there isn’t intimacy in the relationship. The drudgery of everyday life takes intimacy out of relationships. So make the effort to listen to your partner and share with one another the things that happened in your day.

Really listen and get interested. That is really sexy.

Work on the relationship and on validating each other as people. Sex that works is an outgrowth of intimacy, friendship, and trust.