This could be all to pot, but for what it's worth I'm convinced that your mental attitude to a Bleep Test (never done a YoYo) and physical preparation plays a big part.
Over the last year or so, I've done about 5 Bleep Tests and I always seem to do better on the ones where I've known about them a few days in advance, so your preparation is different. Eg just a large coffee and a banana for breakfast (strangely it tastes a lot better than it sounds) no stodge (eg bread) during the day, plenty of water over the day (possibly chuck in a Barrocca tablet) but not too much for the last 3 hours, arrange some distracting music and get it into your head that you're going to do better than you did last time whatever happens.
If you're expecting pain - strangely it's not so bad when you get it. :biggrin: