"He saves planets, rescues civilizations, defeats terrible creatures. And runs a lot. Seriously, there's an outrageous amount of running involved." – Donna Noble in The Doctor's Daughter.
Running
Feet pounding into the ground, blood rushing, adrenaline pumping, both hearts racing…he was running again.
No matter how many times he did this nothing ever killed the thrill of it – the challenge to stay one step ahead of whatever was chasing him, the threat behind him just enough to spur him on, and that life affirming buzz from knowing that he was just managing to evade the grasp of very real danger. Whoever he ran with, whatever he ran from…he couldn't help but enjoy it. No matter how serious the situation there was something about having to run that made him feel very alive.
Maybe he liked it because it symbolised him running into adventure, or perhaps on the flip side it symbolised him running away from the mess he'd made. Or maybe he just liked the physical kick he got out of it.
Whatever the reason, he was very grateful for the fact his life did indeed involve an outrageous amount of running.