跑了很长一段路，一直到了古城堡。这好像很惊奇吧，在我这样的年纪，仍然身体足够健康能在一个下午骑车跑20千米。再过两个礼拜就是我82岁的生日了！我想我(之所以)长寿而且精力充沛，要归功于我过的健康生活。

　　这就是我写信给你的真正原因，我亲爱的孙子。你妈妈告诉我，你不久前开始吸烟了，而且现在你发现很难把它戒掉。相信我吧，我知道开始吸烟是多么容易而戒烟是多么困难。你知道，当我还是一个十几岁的孩子的时候，我也吸过烟，而且对烟还上了瘾。

　　By the way, did you know that this is because you become addicted in three different ways? First⑧， you can become physically addicted to nicotine, which is one of the hundreds of chemicals in cigarettes⑨. This means that after a while your body becomes accustomed to⑩ having nicotine in it. So when the drug leaves your body, you get withdrawal⑪ symptoms. I remember feeling bad­tempered⑫ and sometimes even in pain. Secondly, you become addicted through habit. As you know, if you do the same thing over and over again⑬， you begin to do it automatically⑭. Lastly, you can become mentally⑮ addicted. I believed I was happier and more relaxed after having a cigarette, so I began to think that I could only feel good when I smoked. I was addicted in all three ways, so it was very difficult to quit⑯. But I did⑰ finally manage.

　　⑧first和下文的secondly, lastly等连用，表示顺序。

　　⑨which引导非限制性定语从句，修饰nicotine。

　　⑩accustomed/ə'kʌstəmd/ to 习惯于......

　　⑪withdrawal/wIð'drɔːəl/n.收回；戒毒过程

　　⑫bad­tempered adj.脾气暴躁的；易怒的

　　⑬as引导定语从句，if引导条件状语从句。

　　⑭automatically/ˌɔːtə'mætIklI/adv.无意识地；自动地

　　⑮mentally/'mentəlI/adv.精神上；智力上

　　⑯quit/kwIt/vt.停止(做某事)；离开

　　⑰在"do/does/did＋动词原形"结构中，do/does/did为助动词，意为"确实；的确"，用于肯定句，起加强语气的作用，有人称和时态的变化。

这儿我顺便问你一个问题，你知道上瘾有三个不同方面的原因吗？首先，你会在身体上对尼古丁有瘾，它是香烟里几百种化学物质之一。这就是说，过一段时间以后，你的身体