You've noticed this too eh...
I've learned NEVER to say I'm "thrilled" for exactly the same reason.
I was on a 10 match winning run once, leading by wide margins of between 2 and 5 goals at half-time - also dominating posession, shots,etc...
Each game I tried "Thrilled with performance" and hey presto! My team invariably did'nt bother to perform in the second half.
I've actually found that
"Don't let your performance drop" or
"Pleased with your performance" and even
"Relax - The result will take care of itself" work better :eek:
I'm sure the SI boys and gals will tweek this eventually, as it does have considerable impact on the outcome of games.