You have survived, you have killed, you have saved, you have inspired and yes you have lost.... something has snapped and will never be the same. The definition of love is forever blurred. Real or not real?
The final book in The Hunger Games will pull so many emotions out of you by the time you finish it is almost like becoming an empty shell. Perhaps Collins is giving you a taste of what Katniss had to go through as she barely held onto reality.
The middle of the book slowed and had begun to drag, worry over this turning into just another typical YA surfaces. Then you near the end and the emotional rollercoaster and surprises transform Mockingjay into a book that could change your outlook on life.
After all the blood on her hands and seeing what she has it is not unexpected for Katniss to suffer mentally. It shows her humanity and that she still has it that she is affected so. Near the end when she has to vote (for what will be omitted for the sake of not spoiling it) you really do believe she has lost her mind. Not until after her follow up actions does it become clear she was acting as judge jury and executioner, and Haymitch was smart enough to follow along. It is fitting who Katniss ends up with at the end, they are both scarred and have been broken, but finally united they piece each other back together and find happiness.
The parallel between the Hunger Games and ancient Rome is very strong. The Capital represents Rome perfectly, the indulgence, the cavalier attitude about life, the wastefulness and the love of frivolous fanfare. The Hunger Games serve as a warning to never forget the past least the past repeat itself.