When all hope seems lost, all Dr Forrester cares about is finding Sylvia. And like any good Determinator he never gave up.
Priest: Don't go, son. Stay with us.
Forrester: No, I'm looking for someone. She'll be in a church, standing by the door.
Dr Forrester's last lines sum up the feelings that where most likely being felt by all the people of earth at the end of the film.
Dr Forrester: We prayed for a miracle.
Ray singing "Little Deuce Coupe" as a lullaby to Rachel.
When Ray comes back from killing Ogilvy and Rachel goes over to him and cuddles him, and they fall asleep together.
Also, Ray's reaction upon realizing what he has to do. He walks slowly over to Rachel, as if in a daze, and hugs her as tight as he can. You can practically feel him making his decision in that moment.