One thing that has been mentioned by a couple of posters that I agree with is a lack of confidence we seem to be showing, a lack of belief in ourselves at key times.
Winning games obviously helps that, and part of the problem must be key players and characters from last season missing - Forster, Bertrand, Schneiderlin, Alderweireld, Clyne, - that must be quite a lot of presence and cohesion lost there.