Tenth Doctor: Even if I change it still feels like dying. Everything I am dies. Some new man goes sauntering away... and I'm dead..
(The End of Time - Part 1)
Not any more "a renewal", not just “sort of a way of cheating death (…) I'm gonna change" (in The Parting fo the Ways). The own Tenth Doctor had still hold to such ideas, and he told Rose, when he first showed:
Tenth Doctor: It's me. Honestly, it's me, I was dying. To save my own life I changed my body. Every single cell, but... it's still me.
(Doctor Who: Children in Need 2005)
Yet, very shortly after that, he showed the first signals of a definite, deep change, when he admitted:
Tenth Doctor: I literally do not know who I am. It's all untested. Am I funny? Am I sarcastic? Sexy? Am I an old misery? Life and soul? Right-handed? Left-handed? A gambler? A fighter? A coward? A traitor, a liar, a nervous wreck?
(The Christmas Invasion)
And later revealed, as he discovered it "No second chances, I'm that sort of a man", which started to show us the great difference with his predecessor.
The death of a Doctor has regained dramatic stature: the violence with which Tennant's vital incarnation departed (severely damaging the TARDIS console room!), his previous rebellion against the unfair end:
Tenth Doctor: I’ve gone too far! Is this it? My death? Is it time? No!
(The Waters of Mars)
Yes, he resists: with vehemence and rebellious spirit, first, in that final sentence after Mars, with a pitiful complaint about his untimely departure, as his final words His ultimate acceptance of death (hinted as self-criticism with his "sometimes I think Time Lords live too much" sentence), as even not wanting to leave he chooses to regenerate, unlike the Master in Last of the Time Lords…
All this turns the maybe trivialized act of regeneration into a special issue, core to the character as death is to any person, tragic and philosophical on at least Hamlet's soliloquy’s level:
Hamlet: To be or not to be: that is the question (...) Who would fardels bear, to grunt and sweat under a weary life, but that the dread of something after death, the undiscover'd country from whose bourn no traveller returns, puzzles the will and makes us rather bear those ills we have than fly to others that we know not of?
(Hamlet, III, Scene 1)
Can this be the reason, coupled with his huge vitality, behind the Tenth Doctor's strong rejection of death? It’s a philosophical and moral issue that he had been addressed about: accepting death. Sarah-Jane advised him about accepting others’ death, and he returned her the advice. But accepting your own death… ah, that’s a very different matter. And at the same time, does this link him to his human counterpart, John Smith, and his reluctance to again becoming the Doctor?
 “I don’t want to go!”, The End of Time – Part 2 (2010).
 The End of Time – Part 2 (2010).
 Both John Smith and Donna Noble where shown the possibility of a full life in peace, “the easy way”, him in The Family of Blood (2007), her in Forest of the Dead (2008), and both had to fight the urge for that normal, plenty life.