The way we've taken two key losses in our stride (Manure and Dortmund) suggests we are stronger mentally than in previous years. Promising signs we have eliminated our streakiness, unless it's winning streakiness.
The kind of nervousness that kicks in when you get closer to the prize and are leading the pack is another issue, not one we've really had recently. We know we can chase, we've been doing that plenty, but can we lead from the front? That brings it's own pressures.
My main concern isn't mental though, it's in certain areas where if we lost our starter, our backup would cost us points. That is, Giroud, Sagan and Mertesacker, in order of impact. I think the risks to the two defenders can be largely mitigated with some clever transfer business.
But with Giroud - it's going to be very difficult to get someone in January who would be of the required quality and would slot seamlessly in if Bif were unavailable. Even a footballer as good as Ozil still needs time to adapt. Someone already playing in the Prem would have the best chance so the options are limited.