I totally attribute it to bad play but, and trust me on this, it is always bad luck. It's gotta be. I mean I never make any mistake, ever, and I'm sure this applies to everyone here. But that bleedin river card always catches me out when the pot is way to big for me to fold any two cards.
No sarcasm, I just said something nice, not something just utterly stupid and somewhat funny as I usually do.
So yeah, ignore luck, it's just a technicality. It's all about skill, is it?
Jokes aside, I actually look over everything every time and I try to replay it several times in my head, run the numbers and figure out if I decided correctly or if I should watch out for certain situations in the future. Some losses are perfectly fine and in my opinion if I would win most of the time against most of that cheeky bastard's whole range but lose against that one single hand that beats me, I would repeat my mistake because in the long run, the numbers go in my favour. Of course, some players, some situations, the actions and everything... yeah... it doesn't always work out right, especially in quick fold tables against random fellas, so I stick to ranges. And yes, they do
bluff, stupidly sometimes, not always but I'm often really proud of my hero calls based on my chances "most of the time".