I'm still a bjj newbie (a little under a year), but my own position is that I tend to roll at ~70%. The exact number is of course meaningless, but I basically roll relaxed, make a definate effort to sweep/pass/sub but will let go and move to something else if I sense something isn't working. I.e. I won't spend minutes trying to break a grip or in a pin or whatnot. If someone passes my guard or taps me, it's cool. Try to figure out why it happened and if neccissary, ask upper belts later on to help me with problem areas. However, about once a week or two, I'll come in with the intention of rolling at 100%, basically to make sure I'm still able to get to a mental state where I feel "on" and see where I stand in relation to other folks.
I honestly think the vast majority of my learning happens during the days when I'm conciously rolling lighter. It's not so much a question of ego as one of delayed gratification. I'm kind of at the point where I almost like it when someone taps me repeatedly with a particular technique/set of techniques as it gives me a clear area that I need to improve. Of course it's always better to come back and make them your bitch, but it's equally important to have a clear sense of where your danger positions are. These are the things you get a chance to work on in training.
All that said, a huge part of competition is imposing your own strong points on your opponent, which is almost the exact opposite. Like anything else, you won't get better at that unless you practice it.
So, in other words, your "ego" is a key part of actually putting bjj to use on someone who has other ideas, but make sure you have plenty of "play" time.