Incoming nerd essay
TLDR Pockets are easily tilted mentally because they have a perspective on the game that only applies to them, open pockets even more so.
It's super fucking easy to feel like you are the only one doing anything because you have infinite health and invincibility, you naturally have advantages in fights that your teammates don't get so pockets often lose perspective on how the game actually works. Pretty much all pocket mains who've never spent a fair amount of time on other classes will hit this stage if they're playing on teams that don't have extremely strong players on every slot. This is a thing every pocket that takes 35% or above heals will struggle with, because the game is extremely different with the heal beam. It's also very very easy to get ridiculous stats in open as a pocket and bloat your ego.
The biggest reason pockets don't rape in higher level games is because scouts are really fucking good and shut down aggro soldier play with good movement and aim. In open pockets don't have to deal with that so they get stats that are way better than they would ever be in a higher level. This also lends itself into open pockets thinking they're hot shit because they see themselves doing so well and when they watch higher level games they see invite pockets getting shit on in fights they normally win. They then make the logical fallacy in assuming that they would do better because they've only ever experienced open scouts.
Because of this pockets in open will never be humbled, pockets in open will only get raped by "sandbagging" teams and it's easy to create excuses for yourself when you are in that situation. All pockets that aren't asshole human beings quickly get humbled in IM or Invite because they'll finally encounter scouts that they won't win fights against. They'll realize that invite pockets are much better than them, they just get raped by invite scouts.
Being in open it's pretty easy to get frustrated, you're playing with and against people that are just starting their 6's experience and it's easy to build a major superiority complex when you're raping idiots who haven't got the experience/dm to challenge you personally. Even though I've just written this, I also fall into this mentality when I'm in a particularly annoying game. The heal beam lets you get great stats no matter what and it's easier to blame others than it is to blame yourself.
Trust me when I say that no one wants to be this way. Not getting mad in open is much more difficult than you'd think.