It is clear that the mental differences in each competition are very different and when PSV is in the Champions League, their mentality will be even more drained when facing strong opponents in the round of 16. We know that PSV is very promising in the domestic league but that doesn't necessarily mean the results will be the same when it comes to the Champions League. Dortmund went through a difficult phase in the group stage and they even qualified first as champions in the hell group.
The capacities are different and cannot be compared overall and PSV is still a mediocre team in this competition. I may favor PSV at home but when they are away they won't necessarily be able to beat Dortmund. PSV must win by a fairly large aggregate margin if they want to qualify for the quarterfinals and their success is no more than 20% against Dortmund. I understand that in football it can still happen, but that cannot be used as a benchmark when the opponents are much more experienced in this competition.
There's difference in the intensity of some football contests and it sure affects how the general team's view of the game would be. The UCL is one competition that as the stage advances, the intensity increases and so does the clubs respectively try to blend into the new task ahead. PSV need to get prepared in the task ahead, it's not very easy but there’s no harm in trying.
PSV are doing excellently well overtime in their league, there's no much hike in the league race pressure, they've been able to set right grounds for themselves but situation is different in the UCL, their fate is unpredictable, they just have a glimpse of how their opponent is in their minds and await to see the playing style on the pitch. Their approach to UCL games can't be compared to that of their domestic league and thesame goes for every other club in various contests too.