The David Tennant Treat 4 Today is an interview David Tennant gave about Doctor Who back in 2009.
One of the questions David was asked was how was it to film his last scene as the Tenth Doctor. David's reply was "Emotional. Thrilling, because the scripts are so exciting. You finally get - this character that we do manage to explore, an emotional life for The Doctor that you might not necessarily expect.
Essentially, he has to remain unchanged at the end of each story that the series carries on - but when you get to the point where this version of the character is going to die and he knows he's going to die, the sands of time are running out and the bell is tolling and all those metaphors, you get to take this immutable character to mutable places, and that's very exciting. And emotional, as well.
The character's coming to the end of his life, you're coming to the end of your life on the show, which has been all-consuming. Particularly back home, but all over the world, it's a huge deal. It's very important to people, and particularly to me, all of my life.
So to be moving on from that - and I know I'll never say goodbye to it entirely; I'm sure The Doctor will travel with me as long as I'm on this earth - that's very moving and emotional, and it was to film it."
Link to read the whole interview.