Semi-Ironman here. If I try something and fail because I underestimated the opposition, I live with the consequences. If the AI does something monumentally stupid (like Germany invading India), or the game hits me with some randomly generated disaster on the eve of war for no good reason, I'll reload and try to stop it before it happens.
Case in point: EU3, where I get a randomly spawned rebellion (I've got maximum Stability, zero Revolt Risk in every province, and everyone is happy, yet a revolt breaks out due to a random number generator having a bad day), and that army is way more than double my country's force limit (outnumbered 2:1 by an army that shouldn't exist), and I lose my entire army, I'll reload. Essentially, not reloading means that the rebels take the country, set my national "sliders" back a notch or two, and it'll take me 20-30 years just to get back to where I was. Since I usually play as minor countries, it's just shy of a death sentence. If the wonky "mission" generator hands me a national mission to build a fleet larger than England's and my naval force limit is 2 ships, I reload (over 30 times in that particular instance, before the random stupidity generator gave me a different mission which made slightly more sense). Sorry, but it's not going to happen, and I'd laugh at anyone who even suggested that it's a good idea to bankrupt my modest and mostly inland country to masquerade as the world's leading naval power. If I launch a war against an opponent who turns out to be stronger than me, then it's MY mistake and I live with it. Then there are cases like slightly outnumbering the enemy, having an equal or better general, equivalent techs, and a modest terrain advantage, and getting "stack wiped" because my army rolled either 0 or 1 for all 4 for the first 4 rounds of melee combat, while the opposing army never rolled less than a 7 (which seems to happen repeatedly). By the end of Round Four, my entire army is simply gone. Suffering 1400+ casualties in a single round, while inflicting 30, is absurd. Having it happen repeatedly is insane. It's one thing to lose, another thing to lose so catastrophically that there aren't even any pieces to pick up. That's a "rage quit" moment, followed a day later by a reload of the last save. On the other hand, if I try a naval invasion in HOI3 and my Transports get sunk, it's my mistake, and I play on.
Since I don't do Steam, I won't play HOI4 in Ironman mode, because I probably won't be able to play HOI4 at all. I can still put an old Black Sabbath CD on, and listen to the song.