I think we big ourselves up too much sometimes, especially with football, although this appears to be an English, not a British thing. Quite the opposite of self depreciating.
Every international tournament England qualify for there seems to be a genuine expectation of success and then further genuine horror/surprise when we fail at quite an early stage, just like almost every other football final in history apart from one or two exceptions 
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We would be much better if we went along with the same attitude as the other teams that have never or hardly ever won anything thinking 'yay, we have got to the finals, lets have some fun and maybe we'll get out of the group stages and anything else will be a bonus' but no, the entire country thinks 'we're going to win' and then cries like bad losing children when we get kicked out in the second round, if we make it that far