Wounded pride is an exceptional motivational tool while even the slightest amount of complacency is a very dangerous thing.
There have been a couple of examples recently where the two factors have combined with dramatic results.
An England team so dominant recently against an Australian team with just a single Test victory in 2013 should have meant only one thing.
However, the tourists were blown away by their rampant hosts.
Similarly, just a week after being humbled in their own back garden by Leinster, a hugely fired-up Northampton Saints team gained sweet revenge with one of the most passionate performances you will ever see.
Making amends can be a really positive force.
Yet it is hard to blame either England or Leinster too greatly.
Credit has to go to the side that has dragged itself off the floor.
Having seen their opponents fall so far short of the mark in the most recent encounters neither England nor Leinster could really have expected what followed.
Indeed, unrecognisable are the Australian side today from the ones who were on our shores but a few months ago.
Presumably fed up with the unfamiliar experience of being ridiculed by the old enemy, the Aussies have come out firing in this Ashes series and completely blown away an under-prepared England side who have looked stunned throughout the barrage.
And Saints, third in a two-horse race just over a week ago, put in the most amazing bodies-on-the-line display at the Aviva Stadium and caught the Irish side completely off guard.
Being caught cold like that makes it very hard to respond once the wounded animal has its tail up again.