Don't premove the opening.
I am guessing you premoved 2. Bc4. Ouch.
Then after you lost your bishop, you still tried to play the same moves with your queen, failing to notice that your opponent had protected his pawn...
Double ouch.
You can afford to wait one second to see what your opponent does.
Hey, ya'll! I've been stuck at about the 600's in rating... I never seem to be able to breech the 750's, despite being able to hold long win streaks. Any tips?