During the end of that life, he'd thought only of his friends. Their names and faces and memories; swirling in his mind. Rose. Jack. Mickey. He was leaving them behind to save them. That was a good enough way to go out, he reasoned as the golden light overtook his vision. The last thing he saw with those eyes was Rose Tyler.
At the end of his next life, the Doctor was less content to give up his life for his friends. Why did it always have to be him? Why now when he had so much life left in this Regeneration, so much left to do? As he died to save Wilfred Mott, he was angry with Wilfred and angry with himself. He slunk off into his TARDIS and died alone.
In this life, he died an old, old man to save hundreds. It was his duty to spend what he had thought was his final life there. A debt to pay for the war. A debt for his crimes. The Doctor was glad to do it. He died in his TARDIS again, but not alone. Clara was with him the entire time and he saw Amy one last time. He was ready to go. Ready to start his next life.
At the end of this life, he was fully ready to die. To finally, really end after all these years. He tried to stop his Regeneration for hours. What was the point anymore? What was his worth? The universe would live on with his meddling or his help. He was done. And if he hadn't gotten to talk to the glassy ghosts of his former companions, if Bill and Nardole hadn't convinced him otherwise, if he hadn't remembered Clara, he would've gone through with it, too. The Doctor chose another life after that and he died to start over again.
And she woke again, in her new body, to fire and chaos- and yet she was glad to have done it again. She was glad to continue exploring the universe with her companions. She was glad to save lives and to serve the human race as best she could.
In her most morbid moments though, she sometimes wonders: how will this life end?