In the case of Diastasis Recti, the straight abdominals (the two columns) move away from each other. They are bound together by a sinewy plate that elongates in such case.
If you learn to stretch your belly (the first exercises of Bellyy help you in this), then the two muscle columns will stand close to each other stretched and so they will keep your internal organs inside. If you don’t stretch your abdominals when you do something physically demanding the increased pressure in your belly will push the entrails outwards, which push open the straight abdominals like a trapdoor, further elongating the sinewy plate.
You can pay attention to these right from waking up. It takes extra attention only in the beginning and a few extra seconds, until you think through the movement. After a few weeks, stretching the abdominals becomes natural and almost every move becomes an exercise where you can strengthen your abdominal wall.