I didn't even mind that much until 30 seconds ago when I realized that I had failed to take into account something which affects a short pipe run. Not a big deal if I had caught it -- heck, even a few hours ago. Now I have to run through my calculations again and figure out how much this changes things. The piping design is already done, the profiles are already done and plotted . . . this sucks.
I don't know if I'm cut out to be an engineer. There are just too many little things to remember. I always forget at least one.