Single parents, when did you finally decide that it's totally over and how did you know it's the right time? What were your adjustments?

One of my closest friends is also a single mom who had been in the same situation--deciding when to let go and how to let go. Ive seen her struggle. She was in a rollercoaster kind of relationship with her boyfriend whom, after all that they've been, left her when he knew that she was pregnant. They were still in college that time. She begged for him to stay even just for the baby but he wasnt ready--not for her, not for the baby nor for the responsibility. And then she knew she had enough. She wasnt able to finish her studies due to what happened. she just did what she can to stay healthy during her pregnancy and worked hard to earn and save up for the baby. A year after pregnancy, she went back studying and was able to finish a degree. Now, she is a succesful business woman and mom.