We’d experienced two tough defeats before that home derby - a late 2-1 loss after leading at City and the 5-2 reverse after leading and then losing Emmanuel Adebayor at Arsenal.
Jermain Defoe inspired the 3-1 win at the Lane and since then, we’ve lost just once in 13 matches in the Premier League.
“We had a few difficult games before then and we all felt that,” said Jan. “We played the game like it was the last game of the season.
“We won and everyone had a good feeling afterwards and since then, we’ve only had one defeat, so you can see the impact it had.
“We are fourth in the league and that (top four) was the goal of the club at the beginning of the season, we want to finish there and perhaps even higher.
“If we can get a good result at Upton Park then the next game is Arsenal, so we have to be ready for that and try to keep the run going."
Jan knows we're in for a test tonight though - West Ham have lost just three home matches in the Premier League this term.
“West Ham have the players to beat any team," he added. "I’ve seen a few of their games and every player is strong. We’ll have to be at our best to beat them at Upton Park.”