That happens to me a lot a lot and it is super frustrating. I try not to see it as a reflection on my skill level. If my skill and techniques work on people around my size but don't work on the big guys, I just keep working it as conditioning for next time. I guess my only consolation is knowing what they're doing won't work on many other people... I also try to vary up who I roll with so it doesn't happen constantly... almost everyone at my gym is bigger than me but I try to find more technical guys when I can because it's more fun and they use way less strength (even if they are bigger).
I think the ego is always going to be there but just being aware of it helps.