Many things in this world can and are replaced. There are not many things that are irreplaceable. One of those things is your body. You only get one body so one of your goals should be to have a healthy body.
A healthy body is something where the reward is always worth the work. The more work you put in the bigger the reward will be. There is no way around diet and exercise because you eat everyday and unless your paralyzed you move your body everyday.
For diet, the only thing you have to do is improve and be conscious of whats going in your body. Your diet is your energy and fuel. Just like gasoline in a car you can put in supreme or regular.
The body can be a sports car, tow truck or a mini van depending on how you use it. Your body always steps up to how your challenging it. You will adapt. If you do weights then you will gain muscle. If you run then you will gain cardio. If you do yoga then you will feel good.
The more you put in the more you will get out and the rewards will come immediately.