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My ninth-grade biology teacher would wipe his chalkboard with a smelly wet rag that he only washed when it stuck to the wall. He had other eccentricities as well. When we dissected squid, he preemptively fired up the classroom Bunsen burners. Once we had popped open the ink sac and sketched the tentacles, he told us, we could fry and eat our specimen. I have no idea how many kids ate the thing, because I hightailed it out of there before Mr. H. handed out scalpels.

That wasn’t the only problem my teacher had with me. I refused to clean anything with that dirty towel, and I giggled when he explained plant reproduction. I still remember the “male” pollen-laden stamen, the “female” egg-holding pistil and all the 14-year-old boys joking about flowers getting it on.

Mr. H. kept me after class one day. He sighed and told me he was taking me off the honors science track. There was no point, he explained, because I would never make it to physics. I might even bomb chemistry.

It never occurred to me to question his wisdom. In fact, he gave me an easy out. Why try if it was hopeless? The following year, I didn’t do any of the chemistry homework or take notes in class. I never enrolled in physics. I had no idea I liked science until I took a mandatory geology course my sophomore year of college.

The world tells kids “No, you can’t” in endless ways. They hear it from adults, peers and even from themselves. As a parent and school counselor, I see how easily kids can be derailed. At times, I catch myself discouraging my children from chasing ill-fated goals. My advice may be loving, protective or even sound. But it is equally likely to be premature, misguided or limiting. I try to check myself, to remember that children are perpetually learning and maturing. Setbacks are a necessary part of that journey. As I send my eighth-grade students — and my own son — off to high school, I want them to take risks and move forward with optimism.

Here are 10 key things to teach kids that will help them overcome negativity and quiet their internal defeatist voices:

Bet on yourself. You can’t control anyone else’s thoughts or behavior, but you can count on your own perseverance. Expect success, not because you know more than others, but because you care deeply, and you can trust yourself to put in both the time and effort. Then do it.

Don’t let anyone clip your wings. When Kobe Bryant was 10, his school counselor told him his dream of being an NBA player was unrealistic and he should choose something else. Although that may be solid advice for 99.9 percent of kids, someone will grow up to be a Kobe Bryant. No one can predict the future. Do what inspires you.

Seek forgiveness, not permission. If you ask enough people, eventually you will find someone whose job is to say no. If you know your pursuit is worthwhile, ethical and safe, take a chance. Assume you have a green light until you hear the sirens blaring. It’s a lot easier to stop something than to create something, so make the naysayers work hard to put on the brakes.

Plant yourself where you can grow. You can’t always change your setting, but you can alter the soil. If you are unchallenged, or socially uncomfortable, proactively make adjustments. Rejigger your courses, explore different activities, or shift peer groups.

Illegitimi non carborundum. This fake Latin aphorism means, “Don’t let the bastards grind you down.” The world is full of kind, good and generous people. At times, however, some will treat you with judgment or contempt. Remember that this has nothing to do with you. Choose to be positive, take the high road and maintain your sense of purpose.

When one door closes, open it again. So you tried something that was a complete flop. Maybe you got fired from your first job waiting tables, or you didn’t make the baseball team. It happens. There is no rule that you can never work in a restaurant again or that you can’t try out for the same sport twice. It still may not work out in your favor, but you get to decide how many attempts you can tolerate.

Be vulnerable. If you are unguarded, you risk fear and rejection, but the rewards can be great. Vulnerability is at the root of creativity and innovation. So take that difficult engineering class, try your hand at poetry, or ask out that kid you’ve liked all year.

Don’t define yourself by the external. How you see yourself is different, and often harsher, than how others see you. Remember that there is no one type of beauty, and you are much more than your appearance. Don’t let a negative self-perception stop you from putting yourself out there — whether you want to reach out to a new friend or audition for a play. No one is as focused on you as you think they are.

Practice positive self-talk. People have more than 20,000 thoughts a day, and 80 percent of them are negative. Our brains are hard-wired to pay more attention to bad experiences than to good ones. That can take a toll. You assume that you wouldn’t lie to yourself, but you do. You may be overly self-critical or exaggerate problems. Monitor your thoughts so they don’t hinder you.

Let others do the rejecting. Apply to your favorite college even if your SAT scores seem too low. Enter that fiction contest even though there are hundreds of submissions. Sign up for that tennis match despite being the lowest-ranked player. It may not be a win, but you will never wonder what might have been.

Phyllis L. Fagell is a licensed clinical professional counselor at the Chrysalis Group and a school counselor in Bethesda. She tweets @pfagell.

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