Disclaimer: Just in case anyone thought otherwise, Doctor Who is not mine. :)
When the Doctor takes your hand and tells you to run, you can feel your old life shatter into a million irreplaceable pieces, and it sets your heart on fire- a burning sensation deep inside, an unquenchable longing for adventure, for something more than your small human life. And when the dust settles and you're both laughing in breathless relief, you look at his face and you realize he's the one who put it there.
When the Doctor takes your hand and leads you into his blue box, you just about faint from the shock of it. As you back away through the impossible door, spluttering about bigger-on-the-inside, running once around the impossibly small outside just to make sure, he beams, and the whole world brightens from the radiance of that grin.
When the Doctor takes your hand and leads you onto your first alien world, you cling to him at first, astounded and overwhelmed by the unfamiliar sights and sounds and smells, until you realize that people are people no matter when or where they're from. When you let go and wander off after something or someone catches your eye, you don't feel afraid. If something goes awry, he'll be there to save you. That's what he does.
When the Doctor takes your hand after a day when you can't save everyone and asks if you're all right, you don't answer him at first. And when you gather up the courage to look him in the eye, you feel the force of the sadness there as though it were your own, multiplied by a number you can't even fathom. As you both try to handle your grief, the TARDIS hums soothingly, reminding you that your next adventure is waiting.
When you take the Doctor's hand, he looks at you in faint surprise. He's still not used to being on the receiving end of affection, and that realization makes you so unbearably sad that you throw your arms around him. As you hug him perhaps a little more tightly than necessary, you feel a shaking and hear him start to laugh. At that moment, you realize- this is why you're here. This is one of the most important things you can do: bring joy to the most wonderful man in the universe. After all he has done for you, for everyone, he deserves to be thanked, and your friendship is the best way you know how. For someone who believes that every life is important, he too often overlooks just how much he means to you. To everyone. And in this moment, you vow to go on reminding him for as long as you can. You owe him that much.
You may be just one person, but when the Doctor needs a hand, you'll be there.