I don't want to single anyone out but I don't see how anyone can say there is no such thing as luck. Especially when they then go on to describe the problem as chance and circumstance.
Definition of luck
1
a : A force that brings good fortune or adversity
b : The events or circumstances that operate for or against an individual
2: Favouring chance
You can overcome adversity(bad/biased officiating), you can overcome setbacks(injuries), you have to take advantage of when chance favours you etc I understand all that but it doesn't mean luck doesn't exist or that your are "creating your own luck" completely.
Not in my view anyway, you have to accept that not everything is under your control no matter what you do. The best you can do is reduce or enhance your chances of certain events occurring.
I think we have a manager that does that. We create loads of chances, we concede few chances, we control games(we've done that even against the best teams). We're so used to playing against 12men, to the point where even a bent ref knows when they'll have to take a day off from the agenda because City are giving him nothing to work with. Pep overcomes setbacks such as: Key players being injured, having no natural left back, having no strikers etc consistently and still has success where some managers would be left with nothing and pointing to things that were out of their control.
There's still only so much he can do though. As for mentality, everybody saw Villarreal(7th in La Liga) rattled Liverpool for pretty much the whole of the first half in their home leg. So even the manager who's supposed biggest strength is instilling a strong mentality sees his team rattled(more often than people realise).
Aspects like: When it occurs in the match, what impact it has on the tie(how many of the chances they concede are converted) and how long they have left to regain their composure and turn it around if need be, is all chance.