Gah, my head hurts so much. This is so simple, so why do I keep failing?

All this endless game wants me to do is control 2 Cars racing up four straight lanes, while collecting circular blocks and avoiding round ones. There are no tricks, no confusing controls (a tap to either side of the screen makes the respective car switch lane), and each car has its own pair of tracks - so they can't hit each other.

But over, and over again I crash, unable to unwire and separate each side of my aching brain.