My Warden lost his parents, had to choose between being killed on spot or having a Taint that will eventually turn him into a monster, went to great deal of trouble to save everyone he could, fell in love with a beautiful witch and then learned that final victory will kill him.
At this point Aiden Cousland stopped and thought."Screw this. I did my best to be kind and just, and thats the reward i get? The world has taken enough from me. I won't sacrifice anymore for it. I will live and be happy, damn it! I dont want to die!"
That, and he was curious what's the Old God is like untainted,
Felt the same way in Fallout 3 and because in the words of Scarlett O'Hara, "Tomorrow is another day." If there's a consequence, we can deal with it then. I didn't ask to be a Warden, I was forced by circumstance to become one. I didn't want to die, and I didn't want Alistair to die, so I made him sleep with the witch. My only martyr warden was one who was suicidal because Alistair broke up with her. Those in their right mind choose life every time. Call me whatever you choose, I will still decide to live in that circumstance, and no I don't feel guilty.