"I'll lean on you and you lean on me and we'll be okay."
- Dave Matthews Band

Donna Noble was the Doctor's best friend; there was no doubt about that. She made him laugh, made him question, and made him a lot more human. More than he'd ever desired. Her wry sense of humour and her empathetic outlook on life never faltered.

She had a talent for seeing what wasn't always obvious; and she could spot heartbreak from a mile off. When she first encountered the Doctor, he was dripping with raw emotion and his eyes were full of fiery anguish.

"How'd you mean lost?" She'd asked, her anger subsiding for a while. His desolate stare answered her question. His mind was far away, and Donna soon figured out what his thoughts circled around. He grabbed the purple shirt and threw in over the banister in such a fierce manner that Donna didn't question his actions.

"I can't do it!" She'd squealed, her hands grappling the taxi edge as she positioned herself.

"Trust me," He had replied simply, arms outstretched and his tone confident.

"Is that what you said to her?" Donna had dared to ask, "Your friend, the one you lost. Did she trust you?"

Donna didn't know why she had brought his friend up; maybe her mind was so busy whirring with adrenalin and apprehension that it just spilled out. The Doctor's face had softened, his arms still raised out to her.

"Yes she did. And she's not dead, she is so alive. Now jump!"

And she did. Jumped into his arms to stay alive and jumped into the new life to shed her old image and become a new person.

At their first goodbye, Donna saw another side of the mysterious Time Lord. She saw his eyes melt with memories as he uttered the name of his friend. Rose. He'd flashed Donna a small smile woven with promises and thank yous as he disappeared into the blue box and shot up into the sky. Donna watched, snow falling gently onto her hair and sticking to her skin.

When she found him again after months of searching, she'd imagined that everything would slot back into place. Which it did, eventually. His time with his former companion, Martha Jones, had done him some good; his eyes no longer betrayed as much pain and loss as they had from their previous encounter.

They travelled together, laughing through time and space. She couldn't believe it herself; she was a temp, only good at shorthand, typing and making coffees. It wasn't exactly the perfect life she'd decided to lead after her first encounter with the Doctor. Nor the requried life experience for being the Doctor's companion. But travelling through the stars opened her eyes to a whole other life.

Donna didn't want it to end, but, it did, like all good things. There came a time when Donna could no longer lean on the Doctor for help, because it was too dangerous. She didn't even know who he was, not anymore. And if she ever saw him again, her mind would burn up and she'd have no chance of living any life.

But when the Doctor felt lonely and needed a friend, he'd close his eyes, remember all the times he had with Donna, and then he'd smile. It didn't take away the pain, not entirely, but it was better than nothing.