When Retired Army 1st Sgt. Seth Kastle returned home from his service in Afghanistan and Iraq, he found himself suffering from anger brought on by Post-Traumatic Stress Disorder (PTSD), NBC News reported. To explain his struggle with PTSD to his children, he wrote a book for them, called "Why Is Dad So Mad?" Kastle, who served 16 years in the Army Reserve, crowdfunded more than $6,000 — twice his initial goal — to hire an illustrator and publish the book. "In my book I talk about the fire inside dad's chest. To me, that's what it feels like," Kastle said. And his story has resonated with his 6-year-old daughter, Raegan. "No matter what, when they're mad or sad at you, they still love you," explained Raegan, admiring her father's book in her playroom. "There's always a fire in his heart, but no matter what, I know there's love."