• What you do
• Where you do it
• Who you do it with

and explain why you think doing this is healthy.
 
Possible Answer:
I wake up early in the morning and then walk for an hour every day. After that I swim in the nearby river for about 30 minutes and then I start my day. Waking up very early and then doing the physical exercise is the healthy habit I have developed from the early stage of my life.
I remember my father insisting us to wake up very early and then took us to the nearby high school ground for exercise. Nowadays, I wake up from bed at around 5:30 am and wear my exercise trousers and the pair of shoes. Then I start walking along with the road that has passed beside the river. The fresh air in the morning is very healthy for health. Sometimes I take my bicycle and instead of walking, I ride my cycle. I started doing this early morning exercise and swimming few years back but nowadays 2 of my friends and cousins accompany me almost every day. They enjoy doing the exercise very much.
The morning is a time when the air and environment remain fresher than anytime of the day. So breathing the fresh air, doing the exercises and finally swimming in the fresh water is definitely a very healthy habit. A sound mind lies on a sound body and this habit that I adopted is pretty helpful for keeping a sound health and sound mind.

 

Tips for answering this Cue Card Topic:

Exercise, visiting open and natural places, good food habit etc. are some of the habits which are related to the health. Exercise can vary from going for walking in the morning & evening, running, swimming, cycling, playing outdoor games, and going to gymnasium, doing yoga etc. You can talk about any exercise habit that you have for this cue card as exercise is healthy habit.

Again you can talk about your passion on visiting different places on your vacation as travelling to open spaces gives you mental refreshment as well as help keeping good health.

Finally a good food habit is something positive we can have to maintain a good health. You can talk about your habit of eating vegetable over fishes and meats. Your habit of drinking fruit juice daily is also something health you do. Gardening is a good habit which involved both the passion and physical exercise and can be described as a healthy habit.

Pick an idea related to exercise, good food habit or travelling and talk about that particular topic.

On the other hand, reading books, cooking, listening to music etc. are good for our mental health and thus keeps us joyful which is a healthy habit. If you want to talk about your habit of listening music, painting, cooking or reading, first mention the mental benefits it offers. Then relate the mental health with the physical health and then continue describing the habit.

The second question: "why you do it" and the fourth question "and explain why you think doing this is healthy" are actually similar. For the later one describe the benefits it offer and for the second question mention that  you have a passion on doing it, you spend a quality time this way and you really enjoy doing it. Since the cue card asks you to describe something healthy you enjoy doing, do not only mention the health benefit it offers. You should also talk about why you enjoy it, how passionate you feel about doing it and your involvement on the task.

 
Your preparation for this cue card would also help you answering the following cue card topics:

1. Describe something you enjoy doing.
2. Describe something you do every day.
3. Describe a habit you have.
4. Describe an outdoor activity you have.
5. Describe a game or sports you enjoy playing.
6. Describe a really good habit you have.
7. Describe something you maintain to keep a good health.
8. Talk about something you often do.
9. Describe a place you often go to.
10. Describe something healthy you would recommend your friends.
11. Describe a healthy food item you eat.