I also felt like I should only play through once, so any choices and deaths are final. In my suicide mission I kept everyone alive, apart from jack. Because my Shepard was involved with Miranda I took her side in the jack/Miranda argument. I didn't really care much that jack was pissed at me but when she died I was shocked. She died fighting along my side, just before we reached safety. I felt bad because I would never be able to patch up our argument now. I pretty much felt the exact way you did except yours was about Miranda mine was about jack. Just shows how much a really immersive game with excellent writing can affect us.