Only occasionally. Sometimes I like to make up stories or meta-games involving my units and this makes me get quite attached to them.
Example:
While playing Starcraft 2, I made a reaper towards the end of a team game that I was losing (badly). I named him Stan Lagislaw and made it my goal to get him to the edge of the map, alive, before the game ended. He survived, so I brought him back in the next game (built another reaper). I moved him to an island where he became king of Lagisland. Unfortunately, Lagisland was discovered and Stan was mercilessly slaughtered. I was more than a little upset.
I also like to occasionally make an SCV go out and hunt the npc animals so that he can bring back food to his SCV family.
Example:
While playing Starcraft 2, I made a reaper towards the end of a team game that I was losing (badly). I named him Stan Lagislaw and made it my goal to get him to the edge of the map, alive, before the game ended. He survived, so I brought him back in the next game (built another reaper). I moved him to an island where he became king of Lagisland. Unfortunately, Lagisland was discovered and Stan was mercilessly slaughtered. I was more than a little upset.
I also like to occasionally make an SCV go out and hunt the npc animals so that he can bring back food to his SCV family.