When Ianto started work at Torchwood One, it was just a job, a chance at earning a good wage and setting himself up for the future instead of living hand-to-mouth the way he had been. He’d wanted to make something of himself and he was finally succeeding. Meeting Lisa had been the icing on the cake.
Then everything went to hell in the space of a single day; protecting Lisa had become his only purpose.
When he lost her, the smart thing would’ve been to leave, start over, but Torchwood was in his blood. It was all he had left.