Can you count the seconds of internal, emotional pain? Hermione isn't dealing with the sort of pain that acts like a thief, breaking in, only to leave soon after. It's her whole life and it's ever present doom. There are no vibrant blue seas, but endless rough patches. When one storm has passed another comes. Is it odd that she has gotten a case of sea-sickness? Is it odd that the boat hasn't yet flipped? Is it odd that she may want to jump off the ship?
The last time she relapsed was almost a year ago. She was still a student at Hogwarts, and was still fighting her illness, being raw with her emotions. The useless random fifth and third years sang her songs of childish bullying, while she fell into the arms of Ron Weasley, her knight in shining armor, and she arose powerful beyond all comparison. Ron was her lady of the lake, handing her excalibur to conquer evil. Except that everything was not at all what it seemed.
When the article was written everything changed-people were always watching her, waiting for her cracks to emerge. Strangers gave her looks, and everyone was nicer with their patronizing, encouraging smiles. Understanding nods with little pieces of advice filled her conscience with a brutal reminder that everyone knew. So she learned to handle the stares, to fight the need to cry when she couldn't bare anymore, and to prove to everybody that she was fine.
Ron's comment was poorly thought out, but maybe it needed to be said. It did work, one would assume. She finished her N.E.W.T.S. with amazing marks, and secured a job at the ministry promptly after. Ron found the perfect place for the two of them to live together, right below Harry's and Ginny's. And everybody thought that her demons were gone, that they had disappeared, but what they don't know is plenty. When Ron told her not to break again, when he told her he couldn't "fix her" again. She realized what she felt all along. She was a burden on Ron, and he was tired of helping her. She realized that she needed to get a control on her life, and, when she felt like crap, she needed to deal with life better. Maybe it seemed like a healthy dose of reality, a necessary slap in the face to get Hermione back on track. But, while she visibly got better in order to restore and maintain her relationship with Ron, her heart still ached. She was afraid to let herself be raw with her emotions, instead choosing to internalize every ounce of pain that came her way. Obviously, there were times when she was upset and couldn't help but fall back down. But she was careful to pick herself up, and keep the mask of a successful recovery on her face.
Everyone, including the convincing Hermione herself believed that her breakdown was a thing of the past, and it was. It was, until she slipped and had nobody ready to catch her. And, then, just like that it wasn't. She thought constantly about Ron's words, and knew that she had to deal with it by herself. After all, he would not tolerate another "mistake", and she would not let him consider all of the options. So she tried to forget about the "mistakes", vowing to not let them happen again, except that every time they would re-emerge.
It would be easier if she could just tell someone, and have anybody out there to talk to, to keep her accountable. Yet, she couldn't. If she told Ron, he'd leave. If she told anyone else, they would tell Ron, and he would leave. Clearly, neither solution was an options because Ron leaving would break her heart. She needed Ron like she needed water. Without him, she'd have nothing to live for. And, even if he didn't give up on her, she couldn't tolerate the angst. The couple was finally happy and in love. They were approaching their six month anniversary since they'd rekindled their romance, and it was magical. Hermione simply could not tolerate the risk of having him find out. It outweighed her desire to eliminate all "mistakes".
She reasoned that the "mistakes" were rare. They were just little ones, once in a while. She could handle it. Nobody needed to know.