Mark: Hi, Nam! Nam: Hi, Mark! Long time no see. How are you? Mark: I'm fine, thanks, but you look so fit and healthy! Have you started working out again? Nam: Yes, I have. I've also stopped eating fast food and given up bad habits, such as staying up late. Mark: I can't believe it! I thought you can't live without burgers and chips! Nam: I know. I ate a lot of fast food, but now I prefer fresh fruits and vegetables.  Mark: So what happened? Nam: Well, it was my grandfather. I visited him during my last summer holiday and have learnt a lot of important life lessons from him. Mark: Really? Nam: Yes. He's a wonderful person. He has just had his 90th birthday, but he's still full of energy! Mark: Amazing! How does he stay so active? Nam: Well, he does exercise every morning, goes to bed early, and eats a lot of vegetables. We spent a lot of time together cooking, working in his garden, and walking in the parks. I've learnt from him that taking regular exercise and eating a balanced diet are the key to a long and healthy life.