根据短文内容和所给的中文提示，写出空白处各单词的正确形式，每空限填一词。
I am a middle school student and I'm    (十五）years old, I’m quite healthy.        (然而）, one year ago I was fat. I loved chips and chocolate, and I got tired    （容易地）. One morning, I saw some young men running in the park. They looked really fit and _______(积极的) . So I started running from    （那时）on .
Now I have a 1.5-mile run every morning, I     ( 喝 ) milk and eat fruit and vegetables__________(代替) of chips and chocolate. These good eating habits and running help to build me up. I have great fun running. I feel well and look fit. Running has       (成为) my favorite sport, I'm     （确信）I will do well in the boys' 800-metre race in our school sports meet.
If you want to be healthy,     （加入）us !