I hadn't been on tactics trainer since the site was revised and was completely thrown off by the new timer. While I was working out how it worked my rating dropped almost 200 points! I've almost clawed my way back up again but it made me think about how closely performance and concentration are linked. I've always know vaguely that this was so, but tactics trainer actually put a number to it! When the brain is working at capacity, even small lapses in concentration (like worrying about the timer rather than the problem) are apparently enough to throw off one's game.

I wonder how often our games are affected by things we never think will affect our concentration - alcohol the previous evening, coffee (positive or negative), prescription drugs, lack of sleep, general physical ill health.

This must be a real issue at the top levels of competition, but I'm sure it also holds back lesser players.

Anyone else had this awakening with tactics trainer, and are there any tips on how best to arrive at a game running on all available neurones?

I agree!  When I find myself staring at the TT screen, with no clue what to do, and thinking about something else...I know it's time to end the session and accept the latest 50-pt drop in rating as a lapse in judgment, rather than ability.

There are days I have stepped up to the TT roaring with energy, attention, and concentration - and easily conquer tactic after tactic, and raise my rating up 50-100pts.  The next day, I'll fail 6 in a row, drop another 50-100 pts, and wonder what the hell just happened.  I didn't get dumber over night!

So yes, I think this is a major factor.