Humans keep track of time through recalling important events in their lives. For example, the young boy who fell out of a tree and broke his arm at the age of eight will always remember that incident as a changing point in his life. There is before the fall and after the fall.
Imagine being hospitalized for an asthma attack. During those days you thought you were not going to live. You prayed for release, to be able to draw a breath without pain, day after day. When the tightness in your chest relaxed, you knew then that you were going to live. So there is before the attack and after the attack.
Before the attack you might not have kept your house as clean as the doctor wanted. After the attack you hired a housekeeper who comes in and removes the dust. Before the attack you thought you were allergic to live fir trees, but had one anyway for Christmas. After the attack you bought a fake tree.
Your characters keep track of time in the same way. There is before the robbery and then the capture, trial and jail. There is before the monsters came and then the destruction caused as they swooped over the village and killed hundreds of people. There is before the military coup and then the restrictions that are put into place after the general took charge.
This prompt asks you to write a section of a story in which something happens to your character that changes her life. Something that is large enough to be remembered years after it took place. Nothing is too small or too big. It can be before asking the girl for a date or after the divorce. Before the car accident in which a loved one died or after the prolonged illness of a relative.
So, write down several different life-changing events. Think of as many as possible and save the list for future reference. Choose the one that you think will tell the most compelling story. Then write.