Simply, you have come to terms with the divorce or separation. It can take a long time to reach this stage, and you may have thought that you had accepted things, only to find yourself thrown into one of the other stages unexpectedly. You may bump into an old acquaintance and be back to anger, or even denial. When a person reaches acceptance, they try to make the most of their situation. You may not like what has happened, but you can make decisions that life will go on.
The process of grieving is different for every individual, and should be respected. The time is takes to go through the grieving process varies enormously from individual to individual. It takes a lot longer than you would expect.
It is perfectly normal to bounce back from one stage of the grieving process to another, and then back again.
Getting through the grief can be hard. Be gentle with yourself, and move at a pace that is right for you. Allow yourself to go through the full range of emotions that are part of grief. Learn as much as you can about grief so that you know what to expect. Get adequate support, from family, friends, or even professionals. Sometimes keeping a diary helps, as you can track your progress. Often, people do not realise how much they are changing and growing until they see things written down. Sometimes the opposite is true, and you are stuck but don't realise it. That in itself can be the catalyst for moving on, or seeking help to do so.
However long it takes, it is important to remember that you will get through this.