I'm taking part in a racing simulator league. We have a race every week and I keep improving. This season I'm in a position to win races every now and then, but my problem is concentration. I'm one of the fastest drivers there but hardly ever complete a race without losing my concentration and making costly mistakes.
I know that coffee is supposed to improve concentration but the races are at 22:00 so it's not a good solution for me. Are there any alternatives? Are there any exercises that improve concentration? Any non-prescription substances other than caffeine?