Roberto Martinez believes Everton won the "psychological" battle to overcome Chelsea on Saturday.
The Toffees smashed Jose Mourinho's side 3-1 over the weekend to make it Chelsea's third defeat of the new campaign.
Substitute Steven Naismith scored a hat-trick to sink the west London side, who scored one goal through Nemanja Matic.
And, reflecting on the triumph at Goodison Park, Martinez said: "To cope with everything Chelsea had to throw at us was incredible. To have a clean sheet in the second half is down to the psychology of this group and I’d say that’s down to the last 12 months – the painful experiences of playing in Europe and having to get the mentality right.
"Our form over the 90 minutes deserved the win and that starts to show real good signs of our young players. We looked like a very good team throughout.
"We played a very similar game to what we played 12 months ago. We scored three goals that afternoon and we were a threat going forward. But we were very open and exposed when we didn't have the ball. "Today, we never lost any attacking threat, we were arrogant, and then we restricted Chelsea to two shots on targets in 90 minutes. So that's the difference for me, and probably Chelsea faced a stronger team this time around.
"That has been the strategy behind keeping a group of players in whom we have incredible belief, allowing them to have experiences like the ones that they had in Europe and last season, and the result is there. "I still think we can play a lot better but now you're looking at a complete performance [on Saturday], a complete performance against Southampton and the draw against Spurs now becomes a bit more significant as well."