Myopia progression is a very poorly understood problem and preventing it is difficult.

Definitely many risk factors affect its progression

1. Genetics

2. Amount of near work- extended near work does tend to increase myopia

3. Nutrition- possibly a connection where extremely poor nutrition may lead to increased myopia

4. Age- as it relates to growth - i.e.: puberty and normal human growth

Prevention

1. Pick the right parents

2. Take breaks regularly with close work; make sure your working distance is at least 40 cm or more

3. Eat well, exercise - stay healthy

4. Hope you are done "growing"

There is an entity called progressive myopia, which seems to occur occasionally and seems to have a mind of its own and does indeed result in very large degrees of myopia-it is not known how or why it occurs and often it does so in the absence of all the other risk factors

Hope this helps a bit