Students, as you begin your new school year, I'd like to offer you and your parents some advice from my years in the classroom.

Let me start with Sept. 11, 2001. It was the day terrorists attacked our country, but it was also my first day as a teacher. I had just been hired by a NYC private school. I walked into my new middle-school classroom about an hour before the first plane hit the North Tower.

I didn't get to do much teaching that day. Moreover, the horrors unleashed by terrorists were a precursor to my personal horrors. You see, while I was teaching by day, by night I was drinking, snorting cocaine, having unprotected sex and doing the things you have been warned against. I made bad choices and I allowed them to take over my life.

Despite being in an alcoholic fog most days, I managed to teach. There are former students who still fondly remember their English teacher, Ms. Smith.

I hit bottom in 2009 -- after a two-day bender. I struggled to get sober for two years after that. I've been sober since Sept. 11, 2011 -- 10 years after my first day in the classroom. I'm not proud of having led a double life. In retrospect, I'm amazed that I could function but grateful to be sober.

I don't need to tell you that drinking until you black out and waking up not knowing where you are is poor decision-making. I also don't need to tell you that the best advice is to "just say no." But we know it's not always practical advice.

As one who couldn't "just say no" and cannot "just have one," I can tell you addiction is furiously unforgiving. It'll rob you of your adolescence, poison your 20s and take you hostage in your 30s. For years, you'll wonder what's wrong with yourself. Instead of coping, you'll create permanent solutions to temporary problems. You'll hurt others, but you'll hurt yourself the most.

Parents, talk honestly now with your children about drugs, alcohol, addiction. The last thing you should have to do is talk through these issues while trying to find the best rehab program for your child.

Kids, alcohol and drugs can affect students anywhere -- including classrooms like yours. Some of you may listen to someone give you a similar lecture. Maybe some of you won't pay attention.

I hope you will.

Lisa Smith is writing a memoir about her decade-long battle with addiction while teaching middle school in New York City.