When was the last really important definitive match we won? Not including the Barca first leg as it was not definitive, i.e. we didn't knock them out. I would say Villarreal 2006 (the mad Jens penalty save)
Since then...
2006 Champions League Final v Barcelona LOST
2007 League Cup Final v Chelsea LOST
2008 Champions League QF v Liverpool LOST
2009 Champs league SF v Man U LOST
2009 FA Cup SF v Chelsea LOST
2010 Champions League QF v Barcelona LOST
2011 League Cup Final v Birmingham LOST
2011 Champions League v Barcelona LOST
And that's not including the numerous 'big' league games we've lost such as Birmingham 2008. It's to our shame that we have not won a big match for five years !!! Mental strength.... my arse!!
Shame on you Wenger ....