Derek worked the hardest when there was the most to lose. Whenever there was a child lost, or being hurt. Whenever lives were on the line. Which meant, he gave his all every day.
He had everything he needed to do the job well, but sometimes, stuff got in the way. Garcia got pissed if he put himself in harm's way, but really, he felt like he had lived in harm's way all his life.
More times than not, he woke up sweating, swearing, swinging. Trying to surface from the nightmares so horrific that even all these years later, he still had them. He still remembered. It was haunting and horrible. But sometimes, he did the right thing.
Sometimes, he reached for the phone and called Garcia.
Sometimes, they talked until the sun came up.