I've been playing all games on the highest difficulty possible for years but I've recently scaled it back simply because most developers don't know the difference between challenge and idiocy.
(I like hard games because it forces me to understand the mechanics. If I'm not getting mentally stimulated I quickly grow bored.)
The japanese are generally better at balance. Monster Hunter, Devil May Cry, Dark Souls, anything by Platinun Games.
I think balance means that whenever you die it's clearly your fault. You weren't careful enough, you didn't prepare or maybe you had a shitty build/team because you hadn't bothered to study the mechanics.
If you don't learn anything from dying the balance is bad. You don't have to die either, just taking a bunch of big hits should be enough to make you focus and think about what you're doing wrong. Any lesson is fine, like seeing the callout of a new attack or finding out a particular character is very badly suited for a boss/area.
The worst possible balance is shit that insta-kills you just because, like rocket launchers in Fallout 4 or grenades in Fallout 4 or Legendary Glowing Mirelurks in... you get the point.
So I don't think games should be either hard or easy, I just enjoy games that are both a tactile and mental challenge.
I don't really play games to relax, I just watch Twitch or a show instead if I need to chill.