Re: Star Trek: TMP questions and observations
Decker and Ilia was more Decker made the decision to leave the relationship to avoid being "enslaved" by engaging in a sexual affair with Ilia. Decker left not for the sake of his career, but to protect himself and his independence.
Which makes it all the more interesting that he would sacrifice his independence to help V'Ger at the end of TMP. Granted, we don't know how Decker's personality existed alongside Ilia and V'Ger. But it's interesting that he would leave Ilia to maintain his independence only to sacrifice it to be with Ilia. Perhaps he realized that being with her was what he wanted after all, and he was willing to leave behind his career, his ship, and his life as he had known it in order to make it happen.
"He clapped his captain—his friend—on the shoulder. Yes, this man was very much like James Kirk, in all the ways that mattered." --Christopher L. Bennett-- Star Trek: Mere Anarachy, The Darkness Drops Again