[originaltext]　　If you know something is bad for you, why can’t you just stop?

　　If you know something is bad for you, why can’t you just stop? About 70% of smokers say they would like to stop. Drug and alcohol abusers struggle to give up the bad habits that hurt their bodies and destroy families and friendships. And many of us have unhealthy weight that we could lose if only we would eat right and exercise more. So why don’t we do it? (23) Some scientists have been searching for answers. They’ve studied what happens in our brains as habits form. They’ve found answers to why bad habits, once formed, are so difficult to kick, and they’re developing ways to help us make the changes we’d like to make. Habits are a normal part of life, and are often helpful. We wake up every morning, shower, comb our hair or brush our teeth without being aware of it. We can drive along familiar routes without really thinking about the directions. (24) When behavior become automatic, it gives us an advantage, because the brain does not have to perform the action on purpose. This frees up our brains to focus on different things. (25)One way to kick bad habits is to focus on your unhealthy habits. Then try your best to stop them. For example, habits can be linked in our minds to certain places and activities. You could develop a plan, say, to avoid walking down the hall where there’s a candy machine. Try to avoid going to places where you’ve usually smoked. Stay away from friends and situations linked to problem drinking or drug use. Another helpful way is to replace unhealthy habits with new, healthy ones. But it doesn’t work for everyone.
　　23. What’s the purpose of studying what happens in our brains as habits form?
　　24. Why are habits often of great help to us?
　　25. What should we do if we want to kick bad habits?