A long time ago, billions of years by Gallifrey's personal timeline, I told an old man to choose a singular TARDIS for his and his granddaughter's daring escape. I was not this version of myself then. I didn't know I would be ensuring my own future by that act, but it was possibly the most important decision of any of my lives. I lived and died and lived and died watching over that man through all his lives. Now I stand at the console of my own TARDIS, squeezing every bit of adventure I can out of the universe, before my responsibilities catch up with me... just like him. From time to time, I'll lock on to his TARDIS and materialize a few seconds before him. There's a diner in the area that he doesn't notice and a police box in the area that no one else does. I just need to know he's safe. I need to know he's happy. I will always love him.
I have my own companion now. Ashildr. She prefers to go my the title Me now, but that got too confusing. We compromised. I call her Ash. I couldn't go on my adventures without her. She keeps me from being too reckless. But whether it's the man I silently watch over, or the woman who fights by my side, there are people in my life that I can't bear to lose. That happens, I believe.