Spurs dropping points right after NLD's

Has anyone else noticed this?

Win, lose or draw the gap between Arsenal and tottenham widens right after a North London Derby notably 2012 and this season.

February 2012 spurs were flying and about 10 points ahead of Arsenal and looked like they would finally beat Arsenal to a CL then 5-2 happened. They went on a terrible run, Arsenal closed the gap and eventually overtook them not long after.

7th February 2015 they beat us 2-1 at WHL and go above Arsenal in the table and talks about a North London power begins, 1 week later they go back below us. Forwards 2 months and they are 9 points behind Arsenal and look like a team that has given up.

Are they still suffering the effects of the league cup final? What's happened to their fight?