Imagine you’re 17, 18 or 19 again. You’re programmed to push the envelope, experiment, rebel. You have to, to find out who you are, what you’re capable of, to leave the nest and be able to make it on your own.

Unfortunately, what you have to experiment with in 21st-century America are drugs and alcohol. The drugs are deadlier than ever before, and they’re everywhere. A lot of it’s pharmaceutical, too, Food and Drug Administration-approved, so why not? Why not try taking a handful of pills at a party, or snort some cocaine or heroin? It’s fun, relaxing, you loosen up, get high or just black out.

Imagine next how it could happen to you, how you could go from partying to panhandling, from being a young man full of promise, a young woman with a world of possibilities before her, to an addict, homeless, shooting up in alleyways and hustling to stay alive.

Use opiates for long enough, maybe even as little as a month or two, and you become dependent on them. If you don’t have them, you feel sick, very sick. You need more and more to get high, but you never achieve the original effect.

Meanwhile, your brain is changing, your dopamine is depleted. Soon you find you’re using not to feel good, but to avoid feeling bad, having no energy, no motivation to do anything and getting sick from withdrawal. You start to crave opiates. You become obsessed with seeking them out, and you use them compulsively. You’re in survival mode, and your brain is telling you that you need opiates to survive.

Now, you’re 21 and you’re addicted. You are taking drugs every day just so you can function at the most basic level. You’ve dropped out of college, your parents have kicked you out, you’re living on your best friend’s couch and washing dishes for $9 an hour to get by.

You buy your usual supply of heroin and inject your usual dose. Only this time it’s purer, more potent, or it’s really fentanyl. You go out. You fall on the floor.

Maybe you’re in the bathroom at home or at work, or even in your favorite coffee shop (two recent overdose deaths occurred at Starbucks and Dunkin’ Donuts). If someone else has to use the bathroom, you’re in luck: 911, sirens, Narcan and a trip to the ER. If no one else is around, you’re out of luck, dead.

Next, picture yourself cold, clammy, blue, your breathing’s shallow, barely audible or non-existent. Someone’s given you a shot in your thigh that you can’t even feel. You wake up abruptly, sick as a dog, shaking, sweating, puking, cramping.

The Narcan has displaced the opiates in your brain. Your whole being is in acute withdrawal, and all you want to do is take another shot of heroin to stop it. But some part of you realizes the awful significance of what has just happened. You are stunned that you’ve overdosed, that you actually died and came back. You lived to tell the tale.

This is a turning point for many, many patients. I see them every week at the Milestone Foundation. They’ve just overdosed, and they want to quit. They are desperate for treatment.

And some of them are lucky. They have insurance or a wealthy family, so they can get treatment. But most of them have no choice but to go back to the streets and the shelters. I always ask, “When you leave here, what will you do?” They often answer, “Try not to die.”

Many of the patients I know in recovery on methadone and Suboxone have overdosed, been revived with Narcan and transformed their lives. They get medical treatment and counseling, they reconnect with their families, find jobs. They want things to be better for their kids. They start to dream again, of going back to school, of owning a house. They work hard toward their goals and achieve them.

They tell me that Suboxone or methadone saved their life, or that I did. But it was none of these things. It was an awakening, an epiphany, an act of grace. They realized the enormity of what happened. They saved their own lives. I was lucky enough to be in the right place at the right time to help them.

And Narcan made it possible.