It can be done
Once a person becomes comfortable with counting, it becomes almost second nature. It is not hard to keep track of a winning or a losing streak while counting, or to do other things, like keeping up a conversation, ordering drinks, ogling waitresses, etc.
The more you do it, the easier it becomes. I compare it with driving. Once a person becomes a proficient driver, he or she can drive down the road at 70 mph, keep track of the traffic around him, read the roadsigns, watch for exits, watch for police cars, while at the same time be listening to the radio, carrying on a conversation, and yelling at the kids in the backseat. It comes with time behind the wheel.